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  • Nuclear reactions  (4,460)
  • Photosynthesis  (1,304)
  • Elsevier  (5,166)
  • Springer  (551)
  • Nature Publishing Group (NPG)  (47)
  • American Institute of Physics (AIP)
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  • 1
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    In situ imaging reveals the biomass of giant protists in the global ocean (2016)
    Nature Publishing Group (NPG)
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    Publication Date: 2016-04-21
    Description: Planktonic organisms play crucial roles in oceanic food webs and global biogeochemical cycles. Most of our knowledge about the ecological impact of large zooplankton stems from research on abundant and robust crustaceans, and in particular copepods. A number of the other organisms that comprise planktonic communities are fragile, and therefore hard to sample and quantify, meaning that their abundances and effects on oceanic ecosystems are poorly understood. Here, using data from a worldwide in situ imaging survey of plankton larger than 600 mum, we show that a substantial part of the biomass of this size fraction consists of giant protists belonging to the Rhizaria, a super-group of mostly fragile unicellular marine organisms that includes the taxa Phaeodaria and Radiolaria (for example, orders Collodaria and Acantharia). Globally, we estimate that rhizarians in the top 200 m of world oceans represent a standing stock of 0.089 Pg carbon, equivalent to 5.2% of the total oceanic biota carbon reservoir. In the vast oligotrophic intertropical open oceans, rhizarian biomass is estimated to be equivalent to that of all other mesozooplankton (plankton in the size range 0.2-20 mm). The photosymbiotic association of many rhizarians with microalgae may be an important factor in explaining their distribution. The previously overlooked importance of these giant protists across the widest ecosystem on the planet changes our understanding of marine planktonic ecosystems.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Biard, Tristan -- Stemmann, Lars -- Picheral, Marc -- Mayot, Nicolas -- Vandromme, Pieter -- Hauss, Helena -- Gorsky, Gabriel -- Guidi, Lionel -- Kiko, Rainer -- Not, Fabrice -- England -- Nature. 2016 Apr 28;532(7600):504-7. doi: 10.1038/nature17652. Epub 2016 Apr 20.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Sorbonne Universites, UPMC Universite Paris 06, CNRS, Laboratoire Adaptation et Diversite en Milieu Marin UMR7144, Station Biologique de Roscoff, 29688 Roscoff, France. ; Sorbonne Universites, UPMC Universite Paris 06, CNRS, Laboratoire d'Oceanographie de Villefranche (LOV) UMR7093, Observatoire Oceanologique, 06230 Villefranche-sur-Mer, France. ; GEOMAR Helmholtz Centre for Ocean Research Kiel, Wischhofstrasse 1-3, 24148 Kiel, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/27096373" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Biomass ; *Biota ; Carbon/metabolism ; Carbon Sequestration ; Earth (Planet) ; Microalgae/metabolism ; *Oceans and Seas ; Photosynthesis ; Rhizaria/classification/*isolation & purification/metabolism ; Seawater/chemistry ; Symbiosis ; Zooplankton/classification/*isolation & purification/metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
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    Plankton networks driving carbon export in the oligotrophic ocean (2016)
    Nature Publishing Group (NPG)
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    Publication Date: 2016-02-11
    Description: The biological carbon pump is the process by which CO2 is transformed to organic carbon via photosynthesis, exported through sinking particles, and finally sequestered in the deep ocean. While the intensity of the pump correlates with plankton community composition, the underlying ecosystem structure driving the process remains largely uncharacterized. Here we use environmental and metagenomic data gathered during the Tara Oceans expedition to improve our understanding of carbon export in the oligotrophic ocean. We show that specific plankton communities, from the surface and deep chlorophyll maximum, correlate with carbon export at 150 m and highlight unexpected taxa such as Radiolaria and alveolate parasites, as well as Synechococcus and their phages, as lineages most strongly associated with carbon export in the subtropical, nutrient-depleted, oligotrophic ocean. Additionally, we show that the relative abundance of a few bacterial and viral genes can predict a significant fraction of the variability in carbon export in these regions.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4851848/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4851848/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Guidi, Lionel -- Chaffron, Samuel -- Bittner, Lucie -- Eveillard, Damien -- Larhlimi, Abdelhalim -- Roux, Simon -- Darzi, Youssef -- Audic, Stephane -- Berline, Leo -- Brum, Jennifer R -- Coelho, Luis Pedro -- Espinoza, Julio Cesar Ignacio -- Malviya, Shruti -- Sunagawa, Shinichi -- Dimier, Celine -- Kandels-Lewis, Stefanie -- Picheral, Marc -- Poulain, Julie -- Searson, Sarah -- Tara Oceans Consortium Coordinators -- Stemmann, Lars -- Not, Fabrice -- Hingamp, Pascal -- Speich, Sabrina -- Follows, Mick -- Karp-Boss, Lee -- Boss, Emmanuel -- Ogata, Hiroyuki -- Pesant, Stephane -- Weissenbach, Jean -- Wincker, Patrick -- Acinas, Silvia G -- Bork, Peer -- de Vargas, Colomban -- Iudicone, Daniele -- Sullivan, Matthew B -- Raes, Jeroen -- Karsenti, Eric -- Bowler, Chris -- Gorsky, Gabriel -- England -- Nature. 2016 Apr 28;532(7600):465-70. doi: 10.1038/nature16942. Epub 2016 Feb 10.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Sorbonne Universites, UPMC Universite Paris 06, CNRS, Laboratoire d'oceanographie de Villefranche (LOV), Observatoire Oceanologique, 06230 Villefranche-sur-Mer, France. ; Department of Oceanography, University of Hawaii, Honolulu, Hawaii 96822, USA. ; Department of Microbiology and Immunology, Rega Institute, KU Leuven, Herestraat 49, 3000 Leuven, Belgium. ; Center for the Biology of Disease, VIB, Herestraat 49, 3000 Leuven, Belgium. ; Department of Applied Biological Sciences, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium. ; Sorbonne Universites, UPMC Univ Paris 06, CNRS, Institut de Biologie Paris-Seine (IBPS), Evolution Paris Seine, F-75005, Paris, France. ; Ecole Normale Superieure, PSL Research University, Institut de Biologie de l'Ecole Normale Superieure (IBENS), CNRS UMR 8197, INSERM U1024, 46 rue d'Ulm, F-75005 Paris, France. ; Sorbonne Universites, UPMC Universite Paris 06, CNRS, Laboratoire Adaptation et Diversite en Milieu Marin, Station Biologique de Roscoff, 29680 Roscoff, France. ; LINA UMR 6241, Universite de Nantes, EMN, CNRS, 44322 Nantes, France. ; Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, Arizona 85721, USA. ; Structural and Computational Biology, European Molecular Biology Laboratory, Meyerhofstr. 1, 69117 Heidelberg, Germany. ; Directors' Research European Molecular Biology Laboratory Meyerhofstr. 1, 69117 Heidelberg, Germany. ; CEA - Institut de Genomique, GENOSCOPE, 2 rue Gaston Cremieux, 91057 Evry, France. ; Aix Marseille Universite, CNRS, IGS, UMR 7256, 13288 Marseille, France. ; Department of Geosciences, Laboratoire de Meteorologie Dynamique (LMD), Ecole Normale Superieure, 24 rue Lhomond, 75231 Paris CEDEX 05, France. ; Dept of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA. ; School of Marine Sciences, University of Maine, Orono, Maine 04469, USA. ; Institute for Chemical Research, Kyoto University, Gokasho, Uji, Kyoto, 611-0011, Japan. ; PANGAEA, Data Publisher for Earth and Environmental Science, University of Bremen, 28359 Bremen, Germany. ; MARUM, Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany. ; CNRS, UMR 8030, CP 5706 Evry, France. ; Universite d'Evry, UMR 8030, CP 5706 Evry, France. ; Department of Marine Biology and Oceanography, Institute of Marine Sciences (ICM)-CSIC, Pg. Maritim de la Barceloneta 37-49, Barcelona E0800, Spain. ; Max-Delbruck-Centre for Molecular Medicine, 13092 Berlin, Germany. ; Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Naples, Italy.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26863193" target="_blank"〉PubMed〈/a〉
    Keywords: Aquatic Organisms/genetics/isolation & purification/*metabolism ; Carbon/*metabolism ; Chlorophyll/metabolism ; Dinoflagellida/genetics/isolation & purification/metabolism ; *Ecosystem ; Expeditions ; Genes, Bacterial ; Genes, Viral ; Geography ; Oceans and Seas ; Photosynthesis ; Plankton/genetics/isolation & purification/*metabolism ; Seawater/*chemistry/microbiology/parasitology ; Synechococcus/genetics/isolation & purification/metabolism/virology
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 3
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    Boreal and temperate trees show strong acclimation of respiration to warming (2016)
    Nature Publishing Group (NPG)
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    Publication Date: 2016-03-17
    Description: Plant respiration results in an annual flux of carbon dioxide (CO2) to the atmosphere that is six times as large as that due to the emissions from fossil fuel burning, so changes in either will impact future climate. As plant respiration responds positively to temperature, a warming world may result in additional respiratory CO2 release, and hence further atmospheric warming. Plant respiration can acclimate to altered temperatures, however, weakening the positive feedback of plant respiration to rising global air temperature, but a lack of evidence on long-term (weeks to years) acclimation to climate warming in field settings currently hinders realistic predictions of respiratory release of CO2 under future climatic conditions. Here we demonstrate strong acclimation of leaf respiration to both experimental warming and seasonal temperature variation for juveniles of ten North American tree species growing for several years in forest conditions. Plants grown and measured at 3.4 degrees C above ambient temperature increased leaf respiration by an average of 5% compared to plants grown and measured at ambient temperature; without acclimation, these increases would have been 23%. Thus, acclimation eliminated 80% of the expected increase in leaf respiration of non-acclimated plants. Acclimation of leaf respiration per degree temperature change was similar for experimental warming and seasonal temperature variation. Moreover, the observed increase in leaf respiration per degree increase in temperature was less than half as large as the average reported for previous studies, which were conducted largely over shorter time scales in laboratory settings. If such dampening effects of leaf thermal acclimation occur generally, the increase in respiration rates of terrestrial plants in response to climate warming may be less than predicted, and thus may not raise atmospheric CO2 concentrations as much as anticipated.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Reich, Peter B -- Sendall, Kerrie M -- Stefanski, Artur -- Wei, Xiaorong -- Rich, Roy L -- Montgomery, Rebecca A -- England -- Nature. 2016 Mar 31;531(7596):633-6. doi: 10.1038/nature17142. Epub 2016 Mar 16.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Forest Resources, University of Minnesota, Minnesota 55108, USA. ; Hawkesbury Institute for the Environment, Western Sydney University, Penrith, New South Wales 2753, Australia. ; State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Northwest A&F University, Yangling 712100, China. ; Smithsonian Environmental Research Center, Edgewater, Maryland 20137, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26982730" target="_blank"〉PubMed〈/a〉
    Keywords: *Acclimatization ; Atmosphere ; Carbon Dioxide/metabolism ; Cell Respiration ; Darkness ; *Ecosystem ; Forests ; *Global Warming ; North America ; Photosynthesis ; Plant Leaves/metabolism ; Seasons ; *Temperature ; Time Factors ; Trees/classification/*metabolism
    Print ISSN: 0028-0836
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    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 4
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    Drought impact on forest carbon dynamics and fluxes in Amazonia (2015)
    Nature Publishing Group (NPG)
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    Publication Date: 2015-03-06
    Description: In 2005 and 2010 the Amazon basin experienced two strong droughts, driven by shifts in the tropical hydrological regime possibly associated with global climate change, as predicted by some global models. Tree mortality increased after the 2005 drought, and regional atmospheric inversion modelling showed basin-wide decreases in CO2 uptake in 2010 compared with 2011 (ref. 5). But the response of tropical forest carbon cycling to these droughts is not fully understood and there has been no detailed multi-site investigation in situ. Here we use several years of data from a network of thirteen 1-ha forest plots spread throughout South America, where each component of net primary production (NPP), autotrophic respiration and heterotrophic respiration is measured separately, to develop a better mechanistic understanding of the impact of the 2010 drought on the Amazon forest. We find that total NPP remained constant throughout the drought. However, towards the end of the drought, autotrophic respiration, especially in roots and stems, declined significantly compared with measurements in 2009 made in the absence of drought, with extended decreases in autotrophic respiration in the three driest plots. In the year after the drought, total NPP remained constant but the allocation of carbon shifted towards canopy NPP and away from fine-root NPP. Both leaf-level and plot-level measurements indicate that severe drought suppresses photosynthesis. Scaling these measurements to the entire Amazon basin with rainfall data, we estimate that drought suppressed Amazon-wide photosynthesis in 2010 by 0.38 petagrams of carbon (0.23-0.53 petagrams of carbon). Overall, we find that during this drought, instead of reducing total NPP, trees prioritized growth by reducing autotrophic respiration that was unrelated to growth. This suggests that trees decrease investment in tissue maintenance and defence, in line with eco-evolutionary theories that trees are competitively disadvantaged in the absence of growth. We propose that weakened maintenance and defence investment may, in turn, cause the increase in post-drought tree mortality observed at our plots.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Doughty, Christopher E -- Metcalfe, D B -- Girardin, C A J -- Amezquita, F Farfan -- Cabrera, D Galiano -- Huasco, W Huaraca -- Silva-Espejo, J E -- Araujo-Murakami, A -- da Costa, M C -- Rocha, W -- Feldpausch, T R -- Mendoza, A L M -- da Costa, A C L -- Meir, P -- Phillips, O L -- Malhi, Y -- England -- Nature. 2015 Mar 5;519(7541):78-82. doi: 10.1038/nature14213.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford OX1 3QY, UK. ; Department of Physical Geography and Ecosystem Science, Lund University, Solvegatan 12, 223 62 Lund, Sweden. ; Universidad Nacional San Antonio Abad de Cusco, Apartado Postal Nro 921, Cusco, Peru ; Museo de Historia Natural Noel Kempff Mercado, Universidad Autonoma Gabriel Rene Moreno, Av. Irala 565, Casilla 2489, Santa Cruz, Bolivia. ; Universidade Federal do Para, Instituto de Geociencias, Faculdade de Meteorologia, Rua Augusto Correa, n degrees 01, CEP 66075 - 110, Belem, Para, Brazil. ; IPAM Instituto de Pesquisa Ambiental da Amazonia Rua Horizontina, 104, Centro, 78640-000 Canarana, Mato Grosso, Brazil. ; Department of Geography, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4RJ, UK. ; 1] School of Geosciences, University of Edinburgh, Edinburgh EH9 3FF, UK [2] Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia. ; School of Geography, University of Leeds, Leeds LS2 9JT, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25739631" target="_blank"〉PubMed〈/a〉
    Keywords: Brazil ; Carbon/*metabolism ; Carbon Dioxide/metabolism ; Cell Respiration ; *Droughts ; *Forests ; Photosynthesis ; Trees/cytology/metabolism ; *Tropical Climate
    Print ISSN: 0028-0836
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  • 5
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    Observational determination of surface radiative forcing by CO2 from 2000 to 2010 (2015)
    Nature Publishing Group (NPG)
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    Publication Date: 2015-03-04
    Description: The climatic impact of CO2 and other greenhouse gases is usually quantified in terms of radiative forcing, calculated as the difference between estimates of the Earth's radiation field from pre-industrial and present-day concentrations of these gases. Radiative transfer models calculate that the increase in CO2 since 1750 corresponds to a global annual-mean radiative forcing at the tropopause of 1.82 +/- 0.19 W m(-2) (ref. 2). However, despite widespread scientific discussion and modelling of the climate impacts of well-mixed greenhouse gases, there is little direct observational evidence of the radiative impact of increasing atmospheric CO2. Here we present observationally based evidence of clear-sky CO2 surface radiative forcing that is directly attributable to the increase, between 2000 and 2010, of 22 parts per million atmospheric CO2. The time series of this forcing at the two locations-the Southern Great Plains and the North Slope of Alaska-are derived from Atmospheric Emitted Radiance Interferometer spectra together with ancillary measurements and thoroughly corroborated radiative transfer calculations. The time series both show statistically significant trends of 0.2 W m(-2) per decade (with respective uncertainties of +/-0.06 W m(-2) per decade and +/-0.07 W m(-2) per decade) and have seasonal ranges of 0.1-0.2 W m(-2). This is approximately ten per cent of the trend in downwelling longwave radiation. These results confirm theoretical predictions of the atmospheric greenhouse effect due to anthropogenic emissions, and provide empirical evidence of how rising CO2 levels, mediated by temporal variations due to photosynthesis and respiration, are affecting the surface energy balance.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Feldman, D R -- Collins, W D -- Gero, P J -- Torn, M S -- Mlawer, E J -- Shippert, T R -- England -- Nature. 2015 Mar 19;519(7543):339-43. doi: 10.1038/nature14240. Epub 2015 Feb 25.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Lawrence Berkeley National Laboratory, Earth Sciences Division, 1 Cyclotron Road, MS 74R-316C, Berkeley, California 94720, USA. ; 1] Lawrence Berkeley National Laboratory, Earth Sciences Division, 1 Cyclotron Road, MS 74R-316C, Berkeley, California 94720, USA [2] University of California-Berkeley, Department of Earth and Planetary Science, 307 McCone Hall, MC 4767, Berkeley, California 94720, USA. ; University of Wisconsin-Madison, Space Science and Engineering Center, 1225 W. Dayton Street, Madison, Wisconsin 53706, USA. ; 1] Lawrence Berkeley National Laboratory, Earth Sciences Division, 1 Cyclotron Road, MS 74R-316C, Berkeley, California 94720, USA [2] University of California-Berkeley, Energy and Resources Group, Berkeley, 310 Barrows Hall, MC 3050, California 94720, USA. ; Atmospheric and Environmental Research, Inc., 131 Hartwell Avenue, Lexington, Massachusetts 02141, USA. ; Pacific Northwest National Laboratory, Fundamental and Computational Sciences, 902 Battelle Boulevard, Richland, Washington 99354, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25731165" target="_blank"〉PubMed〈/a〉
    Keywords: Alaska ; Atmosphere/chemistry ; *Carbon Dioxide/analysis ; Cell Respiration ; Greenhouse Effect/statistics & numerical data ; *Infrared Rays ; Models, Theoretical ; *Observation ; Photosynthesis ; Seasons ; Time Factors
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  • 6
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    Expression of barley SUSIBA2 transcription factor yields high-starch low-methane rice (2015)
    Nature Publishing Group (NPG)
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    Publication Date: 2015-07-23
    Description: Atmospheric methane is the second most important greenhouse gas after carbon dioxide, and is responsible for about 20% of the global warming effect since pre-industrial times. Rice paddies are the largest anthropogenic methane source and produce 7-17% of atmospheric methane. Warm waterlogged soil and exuded nutrients from rice roots provide ideal conditions for methanogenesis in paddies with annual methane emissions of 25-100-million tonnes. This scenario will be exacerbated by an expansion in rice cultivation needed to meet the escalating demand for food in the coming decades. There is an urgent need to establish sustainable technologies for increasing rice production while reducing methane fluxes from rice paddies. However, ongoing efforts for methane mitigation in rice paddies are mainly based on farming practices and measures that are difficult to implement. Despite proposed strategies to increase rice productivity and reduce methane emissions, no high-starch low-methane-emission rice has been developed. Here we show that the addition of a single transcription factor gene, barley SUSIBA2 (refs 7, 8), conferred a shift of carbon flux to SUSIBA2 rice, favouring the allocation of photosynthates to aboveground biomass over allocation to roots. The altered allocation resulted in an increased biomass and starch content in the seeds and stems, and suppressed methanogenesis, possibly through a reduction in root exudates. Three-year field trials in China demonstrated that the cultivation of SUSIBA2 rice was associated with a significant reduction in methane emissions and a decrease in rhizospheric methanogen levels. SUSIBA2 rice offers a sustainable means of providing increased starch content for food production while reducing greenhouse gas emissions from rice cultivation. Approaches to increase rice productivity and reduce methane emissions as seen in SUSIBA2 rice may be particularly beneficial in a future climate with rising temperatures resulting in increased methane emissions from paddies.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Su, J -- Hu, C -- Yan, X -- Jin, Y -- Chen, Z -- Guan, Q -- Wang, Y -- Zhong, D -- Jansson, C -- Wang, F -- Schnurer, A -- Sun, C -- England -- Nature. 2015 Jul 30;523(7562):602-6. doi: 10.1038/nature14673. Epub 2015 Jul 22.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Institute of Biotechnology, Fujian Academy of Agricultural Sciences, Fuzhou 350003, China [2] Department of Plant Biology, Uppsala BioCenter, Linnean Center for Plant Biology, Swedish University of Agricultural Sciences, PO Box 7080, SE-75007 Uppsala, Sweden. ; Department of Plant Biology, Uppsala BioCenter, Linnean Center for Plant Biology, Swedish University of Agricultural Sciences, PO Box 7080, SE-75007 Uppsala, Sweden. ; 1] Department of Plant Biology, Uppsala BioCenter, Linnean Center for Plant Biology, Swedish University of Agricultural Sciences, PO Box 7080, SE-75007 Uppsala, Sweden [2] Hunan Provincial Key Laboratory of Crop Germplasm Innovation and Utilization, Hunan Agricultural University, Changsha 410128, China. ; Institute of Biotechnology, Fujian Academy of Agricultural Sciences, Fuzhou 350003, China. ; The Environmental Molecular Sciences Laboratory (EMSL), Pacific Northwest National Laboratory, PO Box 999, K8-93 Richland, Washington 99352, USA. ; Department of Microbiology, Uppsala BioCenter, Swedish University of Agricultural Sciences, SE-75007 Uppsala, Sweden.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26200336" target="_blank"〉PubMed〈/a〉
    Keywords: Agriculture/methods/trends ; Atmosphere/chemistry ; Biomass ; Carbon Cycle ; China ; Conservation of Natural Resources/methods ; Food Supply/methods ; Genotype ; Global Warming/prevention & control ; Greenhouse Effect/*prevention & control ; Hordeum/*genetics ; Methane/biosynthesis/*metabolism ; Molecular Sequence Data ; Oryza/genetics/growth & development/*metabolism ; Phenotype ; Photosynthesis ; Plant Components, Aerial/metabolism ; Plant Proteins/genetics/*metabolism ; Plant Roots/metabolism ; Plants, Genetically Modified ; Rhizosphere ; Seeds/metabolism ; Starch/biosynthesis/*metabolism ; Transcription Factors/genetics/*metabolism
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  • 7
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    Interaction and signalling between a cosmopolitan phytoplankton and associated bacteria (2015)
    Nature Publishing Group (NPG)
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    Publication Date: 2015-05-29
    Description: Interactions between primary producers and bacteria impact the physiology of both partners, alter the chemistry of their environment, and shape ecosystem diversity. In marine ecosystems, these interactions are difficult to study partly because the major photosynthetic organisms are microscopic, unicellular phytoplankton. Coastal phytoplankton communities are dominated by diatoms, which generate approximately 40% of marine primary production and form the base of many marine food webs. Diatoms co-occur with specific bacterial taxa, but the mechanisms of potential interactions are mostly unknown. Here we tease apart a bacterial consortium associated with a globally distributed diatom and find that a Sulfitobacter species promotes diatom cell division via secretion of the hormone indole-3-acetic acid, synthesized by the bacterium using both diatom-secreted and endogenous tryptophan. Indole-3-acetic acid and tryptophan serve as signalling molecules that are part of a complex exchange of nutrients, including diatom-excreted organosulfur molecules and bacterial-excreted ammonia. The potential prevalence of this mode of signalling in the oceans is corroborated by metabolite and metatranscriptome analyses that show widespread indole-3-acetic acid production by Sulfitobacter-related bacteria, particularly in coastal environments. Our study expands on the emerging recognition that marine microbial communities are part of tightly connected networks by providing evidence that these interactions are mediated through production and exchange of infochemicals.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Amin, S A -- Hmelo, L R -- van Tol, H M -- Durham, B P -- Carlson, L T -- Heal, K R -- Morales, R L -- Berthiaume, C T -- Parker, M S -- Djunaedi, B -- Ingalls, A E -- Parsek, M R -- Moran, M A -- Armbrust, E V -- England -- Nature. 2015 Jun 4;522(7554):98-101. doi: 10.1038/nature14488. Epub 2015 May 27.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] School of Oceanography, University of Washington, Seattle, Washington 98195, USA [2] Chemistry Faculty, New York University Abu Dhabi, PO Box 129188, Abu Dhabi, United Arab Emirates. ; Department of Microbiology, University of Washington, Seattle, Washington 98195, USA. ; School of Oceanography, University of Washington, Seattle, Washington 98195, USA. ; Department of Microbiology, University of Georgia, Athens, Georgia 30602, USA. ; Department of Marine Science, University of Georgia, Athens, Georgia 30602, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26017307" target="_blank"〉PubMed〈/a〉
    Keywords: Diatoms/cytology/genetics/*metabolism/*microbiology ; *Ecosystem ; Indoleacetic Acids/*metabolism ; Metabolomics ; Molecular Sequence Data ; Oceans and Seas ; Photosynthesis ; Phytoplankton/cytology/genetics/*metabolism/*microbiology ; Rhodobacteraceae/genetics/*metabolism ; Seawater/chemistry ; Transcriptome ; Tryptophan/metabolism
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  • 8
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    In retrospect: A century of phage lessons (2015)
    Nature Publishing Group (NPG)
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    Publication Date: 2015-12-04
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rohwer, Forest -- Segall, Anca M -- England -- Nature. 2015 Dec 3;528(7580):46-8. doi: 10.1038/528046a.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Viral Information Institute, Department of Biology, San Diego State University, San Diego, California 92182, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26632584" target="_blank"〉PubMed〈/a〉
    Keywords: *Bacteriophages/genetics/immunology/pathogenicity/physiology ; CRISPR-Cas Systems/genetics ; Cyanobacteria/genetics/metabolism/virology ; Evolution, Molecular ; Gene Transfer, Horizontal/genetics ; Genome, Viral/genetics ; History, 20th Century ; History, 21st Century ; Host-Pathogen Interactions/genetics ; Humans ; Molecular Biology/*history ; Mutagenesis/genetics ; Neoplasms/genetics/pathology ; Oncogenes/genetics ; Photosynthesis ; Sequence Analysis, DNA/history ; Synthetic Biology/trends
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    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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    Ocean biogeochemistry: Carbon at the coastal interface (2014)
    Nature Publishing Group (NPG)
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    Publication Date: 2014-12-10
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gruber, Nicolas -- England -- Nature. 2015 Jan 8;517(7533):148-9. doi: 10.1038/nature14082. Epub 2014 Dec 10.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Environmental Physics Group, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, 8092 Zurich, Switzerland.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25487156" target="_blank"〉PubMed〈/a〉
    Keywords: Aquatic Organisms/metabolism ; Atmosphere/chemistry ; Carbon Dioxide/*analysis ; *Carbon Sequestration ; *Ecosystem ; Human Activities ; *Oceans and Seas ; Photosynthesis
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    The rise of oxygen in Earth's early ocean and atmosphere (2014)
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    Publication Date: 2014-02-21
    Description: The rapid increase of carbon dioxide concentration in Earth's modern atmosphere is a matter of major concern. But for the atmosphere of roughly two-and-half billion years ago, interest centres on a different gas: free oxygen (O2) spawned by early biological production. The initial increase of O2 in the atmosphere, its delayed build-up in the ocean, its increase to near-modern levels in the sea and air two billion years later, and its cause-and-effect relationship with life are among the most compelling stories in Earth's history.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lyons, Timothy W -- Reinhard, Christopher T -- Planavsky, Noah J -- England -- Nature. 2014 Feb 20;506(7488):307-15. doi: 10.1038/nature13068.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth Sciences, University of California, Riverside, California 92521, USA. ; 1] Department of Earth Sciences, University of California, Riverside, California 92521, USA [2] Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA [3] School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia 30332, USA. ; 1] Department of Earth Sciences, University of California, Riverside, California 92521, USA [2] Department of Geology and Geophysics, Yale University, New Haven, Connecticut 06511, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24553238" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Atmosphere/*chemistry ; *Earth (Planet) ; *Evolution, Chemical ; History, Ancient ; Life ; Oxygen/analysis/history/*metabolism ; Photosynthesis ; Seawater/*chemistry
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    Widespread decline of Congo rainforest greenness in the past decade (2014)
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    Publication Date: 2014-04-25
    Description: Tropical forests are global epicentres of biodiversity and important modulators of climate change, and are mainly constrained by rainfall patterns. The severe short-term droughts that occurred recently in Amazonia have drawn attention to the vulnerability of tropical forests to climatic disturbances. The central African rainforests, the second-largest on Earth, have experienced a long-term drying trend whose impacts on vegetation dynamics remain mostly unknown because in situ observations are very limited. The Congolese forest, with its drier conditions and higher percentage of semi-evergreen trees, may be more tolerant to short-term rainfall reduction than are wetter tropical forests, but for a long-term drought there may be critical thresholds of water availability below which higher-biomass, closed-canopy forests transition to more open, lower-biomass forests. Here we present observational evidence for a widespread decline in forest greenness over the past decade based on analyses of satellite data (optical, thermal, microwave and gravity) from several independent sensors over the Congo basin. This decline in vegetation greenness, particularly in the northern Congolese forest, is generally consistent with decreases in rainfall, terrestrial water storage, water content in aboveground woody and leaf biomass, and the canopy backscatter anomaly caused by changes in structure and moisture in upper forest layers. It is also consistent with increases in photosynthetically active radiation and land surface temperature. These multiple lines of evidence indicate that this large-scale vegetation browning, or loss of photosynthetic capacity, may be partially attributable to the long-term drying trend. Our results suggest that a continued gradual decline of photosynthetic capacity and moisture content driven by the persistent drying trend could alter the composition and structure of the Congolese forest to favour the spread of drought-tolerant species.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zhou, Liming -- Tian, Yuhong -- Myneni, Ranga B -- Ciais, Philippe -- Saatchi, Sassan -- Liu, Yi Y -- Piao, Shilong -- Chen, Haishan -- Vermote, Eric F -- Song, Conghe -- Hwang, Taehee -- England -- Nature. 2014 May 1;509(7498):86-90. doi: 10.1038/nature13265. Epub 2014 Apr 23.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Atmospheric and Environmental Sciences, University at Albany, State University of New York (SUNY), Albany, New York 12222, USA. ; I. M. Systems Group (IMSG), National Oceanic and Atmospheric Administration/National Environmental Satellite, Data, and Information Service/The Center for Satellite Applications and Research (NOAA/NESDIS/STAR), 5830 University Research Court, College Park, Maryland 20740, USA. ; Department of Earth and Environment, Boston University, Boston, Massachusetts 02215, USA. ; Laboratoire des Sciences du Climat et de l'Environnement (LSCE), CEA-CNRS-UVSQ, 91191 Gif sur Yvette Cedex, France. ; Jet Propulsion Laboratory, Pasadena, California 91109, USA. ; ARC Centre of Excellence for Climate Systems Science & Climate Change Research Centre, University of New South Wales, Sydney, New South Wales 2052, Australia. ; Department of Ecology, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China. ; Key Laboratory of Meteorological Disaster, Ministry of Education, Nanjing University of Information Science and Technology, Nanjing 210044, China. ; NASA Goddard Space Flight Center, Code 619, Greenbelt, Maryland 20771, USA. ; 1] Department of Geography, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 29599, USA [2] School of Forestry and Landscape Architecture, Anhui Agricultural University, Hefei, Anhui 230036, China. ; Institute for the Environment, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 29599, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24759324" target="_blank"〉PubMed〈/a〉
    Keywords: Acclimatization ; Biodiversity ; Biomass ; Chlorophyll/analysis/metabolism ; Climate Change/*statistics & numerical data ; Congo ; Droughts/statistics & numerical data ; Photosynthesis ; Plant Leaves/*growth & development/metabolism ; *Rain ; Satellite Imagery ; Seasons ; Temperature ; Time Factors ; Trees/*growth & development/metabolism ; *Tropical Climate ; Water/analysis/metabolism ; Wood/growth & development/metabolism
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    Amazon forests maintain consistent canopy structure and greenness during the dry season (2014)
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    Publication Date: 2014-02-07
    Description: The seasonality of sunlight and rainfall regulates net primary production in tropical forests. Previous studies have suggested that light is more limiting than water for tropical forest productivity, consistent with greening of Amazon forests during the dry season in satellite data. We evaluated four potential mechanisms for the seasonal green-up phenomenon, including increases in leaf area or leaf reflectance, using a sophisticated radiative transfer model and independent satellite observations from lidar and optical sensors. Here we show that the apparent green up of Amazon forests in optical remote sensing data resulted from seasonal changes in near-infrared reflectance, an artefact of variations in sun-sensor geometry. Correcting this bidirectional reflectance effect eliminated seasonal changes in surface reflectance, consistent with independent lidar observations and model simulations with unchanging canopy properties. The stability of Amazon forest structure and reflectance over seasonal timescales challenges the paradigm of light-limited net primary production in Amazon forests and enhanced forest growth during drought conditions. Correcting optical remote sensing data for artefacts of sun-sensor geometry is essential to isolate the response of global vegetation to seasonal and interannual climate variability.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Morton, Douglas C -- Nagol, Jyoteshwar -- Carabajal, Claudia C -- Rosette, Jacqueline -- Palace, Michael -- Cook, Bruce D -- Vermote, Eric F -- Harding, David J -- North, Peter R J -- England -- Nature. 2014 Feb 13;506(7487):221-4. doi: 10.1038/nature13006. Epub 2014 Feb 5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA. ; 1] University of Maryland, College Park, Department of Geographical Sciences, College Park, Maryland 20742, USA [2] Global Land Cover Facility, College Park, Maryland 20740, USA. ; 1] NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA [2] Sigma Space Corporation, Lantham, Maryland 20706, USA. ; 1] NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA [2] University of Maryland, College Park, Department of Geographical Sciences, College Park, Maryland 20742, USA [3] Swansea University, Department of Geography, Singleton Park, Swansea SA2 8PP, UK. ; Earth System Research Center, University of New Hampshire, Durham, New Hampshire 03824, USA. ; Swansea University, Department of Geography, Singleton Park, Swansea SA2 8PP, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24499816" target="_blank"〉PubMed〈/a〉
    Keywords: Artifacts ; Brazil ; Color ; *Droughts ; Ecosystem ; Fresh Water/analysis ; Models, Biological ; Photosynthesis ; Pigmentation/*physiology ; Plant Leaves/anatomy & histology/growth & development/*physiology ; Rain ; Satellite Imagery ; *Seasons ; *Sunlight ; Trees/anatomy & histology/growth & development/*physiology ; *Tropical Climate
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    Agribiotechnology: Blue-sky rice (2014)
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    Publication Date: 2014-11-05
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Dayton, Leigh -- England -- Nature. 2014 Oct 30;514(7524):S52-4.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25368887" target="_blank"〉PubMed〈/a〉
    Keywords: Agriculture/*methods/trends ; Australia ; Biotechnology/*trends ; Crops, Agricultural/genetics/growth & development/microbiology/supply & ; distribution ; Fertilizers ; Food Supply ; Nitrogen/metabolism ; Oryza/*genetics/growth & development/microbiology/*supply & distribution ; Photosynthesis ; Plant Diseases/genetics/microbiology
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    Methane fluxes show consistent temperature dependence across microbial to ecosystem scales (2014)
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    Publication Date: 2014-03-29
    Description: Methane (CH4) is an important greenhouse gas because it has 25 times the global warming potential of carbon dioxide (CO2) by mass over a century. Recent calculations suggest that atmospheric CH4 emissions have been responsible for approximately 20% of Earth's warming since pre-industrial times. Understanding how CH4 emissions from ecosystems will respond to expected increases in global temperature is therefore fundamental to predicting whether the carbon cycle will mitigate or accelerate climate change. Methanogenesis is the terminal step in the remineralization of organic matter and is carried out by strictly anaerobic Archaea. Like most other forms of metabolism, methanogenesis is temperature-dependent. However, it is not yet known how this physiological response combines with other biotic processes (for example, methanotrophy, substrate supply, microbial community composition) and abiotic processes (for example, water-table depth) to determine the temperature dependence of ecosystem-level CH4 emissions. It is also not known whether CH4 emissions at the ecosystem level have a fundamentally different temperature dependence than other key fluxes in the carbon cycle, such as photosynthesis and respiration. Here we use meta-analyses to show that seasonal variations in CH4 emissions from a wide range of ecosystems exhibit an average temperature dependence similar to that of CH4 production derived from pure cultures of methanogens and anaerobic microbial communities. This average temperature dependence (0.96 electron volts (eV)), which corresponds to a 57-fold increase between 0 and 30 degrees C, is considerably higher than previously observed for respiration (approximately 0.65 eV) and photosynthesis (approximately 0.3 eV). As a result, we show that both the emission of CH4 and the ratio of CH4 to CO2 emissions increase markedly with seasonal increases in temperature. Our findings suggest that global warming may have a large impact on the relative contributions of CO2 and CH4 to total greenhouse gas emissions from aquatic ecosystems, terrestrial wetlands and rice paddies.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Yvon-Durocher, Gabriel -- Allen, Andrew P -- Bastviken, David -- Conrad, Ralf -- Gudasz, Cristian -- St-Pierre, Annick -- Thanh-Duc, Nguyen -- del Giorgio, Paul A -- England -- Nature. 2014 Mar 27;507(7493):488-91. doi: 10.1038/nature13164. Epub 2014 Mar 19.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Environment and Sustainability Institute, University of Exeter, Penryn, Cornwall, TR10 9EZ. UK. ; Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia. ; Department of Thematic Studies - Water and Environmental Studies, Linkoping University, SE-581 83 Linkoping, Sweden. ; Max-Planck-Institute for Terrestrial Microbiology, Karl-von-Frisch-Strasse 10, 35043 Marburg, Germany. ; 1] Department of Ecology and Environmental Sciences, Umea University, Linnaeus vag 6, SE-901 87 Umea, Sweden [2] Department of Ecology and Genetics, Limnology, Uppsala University, Norbyvagen 18D, SE-752 36, Uppsala Sweden [3] Department of Ecology and Evolutionary Biology, Princeton University, Princeton, 106A Guyot Hall, New Jersey 08544, USA. ; Departement des sciences biologiques, Universite du Quebec a Montreal, Montreal, Province of Quebec, H2X 3X8, Canada. ; Earth Systems Research Center, Institute for the Study of Earth, Oceans, and Space, University of New Hampshire, Durham, New Hampshire 03824, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24670769" target="_blank"〉PubMed〈/a〉
    Keywords: Anaerobiosis ; Aquatic Organisms/metabolism ; Archaea/*metabolism ; Atmosphere/chemistry ; Carbon Cycle ; Carbon Dioxide/analysis ; Cell Respiration ; *Ecosystem ; Geologic Sediments/microbiology ; *Global Warming ; Greenhouse Effect ; Methane/analysis/*metabolism ; Oryza/metabolism ; Photosynthesis ; Seasons ; *Temperature ; Wetlands
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    NASA carbon-monitoring orbiter readies for launch (2014)
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    Publication Date: 2014-06-27
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Morello, Lauren -- England -- Nature. 2014 Jun 26;510(7506):451-2. doi: 10.1038/510451a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24965628" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere/chemistry ; Carbon Dioxide/*analysis ; Environmental Monitoring/*instrumentation ; Fossil Fuels ; *Geographic Mapping ; *Greenhouse Effect ; Luminescent Measurements/instrumentation ; Photosynthesis ; Plants/metabolism ; Satellite Imagery/*instrumentation ; United States ; United States National Aeronautics and Space Administration
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    Drought sensitivity of Amazonian carbon balance revealed by atmospheric measurements (2014)
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    Publication Date: 2014-02-07
    Description: Feedbacks between land carbon pools and climate provide one of the largest sources of uncertainty in our predictions of global climate. Estimates of the sensitivity of the terrestrial carbon budget to climate anomalies in the tropics and the identification of the mechanisms responsible for feedback effects remain uncertain. The Amazon basin stores a vast amount of carbon, and has experienced increasingly higher temperatures and more frequent floods and droughts over the past two decades. Here we report seasonal and annual carbon balances across the Amazon basin, based on carbon dioxide and carbon monoxide measurements for the anomalously dry and wet years 2010 and 2011, respectively. We find that the Amazon basin lost 0.48 +/- 0.18 petagrams of carbon per year (Pg C yr(-1)) during the dry year but was carbon neutral (0.06 +/- 0.1 Pg C yr(-1)) during the wet year. Taking into account carbon losses from fire by using carbon monoxide measurements, we derived the basin net biome exchange (that is, the carbon flux between the non-burned forest and the atmosphere) revealing that during the dry year, vegetation was carbon neutral. During the wet year, vegetation was a net carbon sink of 0.25 +/- 0.14 Pg C yr(-1), which is roughly consistent with the mean long-term intact-forest biomass sink of 0.39 +/- 0.10 Pg C yr(-1) previously estimated from forest censuses. Observations from Amazonian forest plots suggest the suppression of photosynthesis during drought as the primary cause for the 2010 sink neutralization. Overall, our results suggest that moisture has an important role in determining the Amazonian carbon balance. If the recent trend of increasing precipitation extremes persists, the Amazon may become an increasing carbon source as a result of both emissions from fires and the suppression of net biome exchange by drought.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Gatti, L V -- Gloor, M -- Miller, J B -- Doughty, C E -- Malhi, Y -- Domingues, L G -- Basso, L S -- Martinewski, A -- Correia, C S C -- Borges, V F -- Freitas, S -- Braz, R -- Anderson, L O -- Rocha, H -- Grace, J -- Phillips, O L -- Lloyd, J -- England -- Nature. 2014 Feb 6;506(7486):76-80. doi: 10.1038/nature12957.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] Instituto de Pesquisas Energeticas e Nucleares (IPEN)-Comissao Nacional de Energia Nuclear (CNEN)-Atmospheric Chemistry Laboratory, 2242 Avenida Professor Lineu Prestes, Cidade Universitaria, Sao Paulo CEP 05508-000, Brazil [2]. ; 1] School of Geography, University of Leeds, Woodhouse Lane, Leeds LS9 2JT, UK [2]. ; 1] Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, 325 Broadway, Boulder, Colorado 80305, USA [2] Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado, Boulder, Colorado 80309, USA [3]. ; Environmental Change Institute, School of Geography and the Environment, University of Oxford, South Parks Road, Oxford OX1 3QY, UK. ; Instituto de Pesquisas Energeticas e Nucleares (IPEN)-Comissao Nacional de Energia Nuclear (CNEN)-Atmospheric Chemistry Laboratory, 2242 Avenida Professor Lineu Prestes, Cidade Universitaria, Sao Paulo CEP 05508-000, Brazil. ; Center for Weather Forecasts and Climate Studies, Instituto Nacional de Pesquisas Espaciais (INPE), Rodovia Dutra, km 39, Cachoeira Paulista CEP 12630-000, Brazil. ; 1] Environmental Change Institute, School of Geography and the Environment, University of Oxford, South Parks Road, Oxford OX1 3QY, UK [2] Remote Sensing Division, INPE (National Institute for Space Research), 1758 Avenida dos Astronautas, Sao Jose dos Campos CEP 12227-010, Brazil. ; Departamento de Ciencias Atmosfericas/Instituto de Astronomia e Geofisica (IAG)/Universidade de Sao Paulo, 1226 Rua do Matao, Cidade Universitaria, Sao Paulo CEP 05508-090, Brazil. ; Crew Building, The King's Buildings, West Mains Road, Edinburgh EH9 3JN, UK. ; School of Geography, University of Leeds, Woodhouse Lane, Leeds LS9 2JT, UK. ; 1] School of Tropical and Marine Biology and Centre for Terrestrial Environmental and Sustainability Sciences, James Cook University, Cairns 4870, Queensland, Australia [2] Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot SL5 7PY, Berkshire, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24499918" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere/*chemistry ; Biomass ; Biota ; Brazil ; *Carbon Cycle ; Carbon Dioxide/analysis ; Carbon Monoxide/analysis ; Droughts/*statistics & numerical data ; Fires/statistics & numerical data ; Fresh Water/analysis ; Photosynthesis ; Rain ; Seasons ; Trees/metabolism ; Tropical Climate
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    Long-term warming restructures Arctic tundra without changing net soil carbon storage (2013)
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    Publication Date: 2013-05-17
    Description: High latitudes contain nearly half of global soil carbon, prompting interest in understanding how the Arctic terrestrial carbon balance will respond to rising temperatures. Low temperatures suppress the activity of soil biota, retarding decomposition and nitrogen release, which limits plant and microbial growth. Warming initially accelerates decomposition, increasing nitrogen availability, productivity and woody-plant dominance. However, these responses may be transitory, because coupled abiotic-biotic feedback loops that alter soil-temperature dynamics and change the structure and activity of soil communities, can develop. Here we report the results of a two-decade summer warming experiment in an Alaskan tundra ecosystem. Warming increased plant biomass and woody dominance, indirectly increased winter soil temperature, homogenized the soil trophic structure across horizons and suppressed surface-soil-decomposer activity, but did not change total soil carbon or nitrogen stocks, thereby increasing net ecosystem carbon storage. Notably, the strongest effects were in the mineral horizon, where warming increased decomposer activity and carbon stock: a 'biotic awakening' at depth.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sistla, Seeta A -- Moore, John C -- Simpson, Rodney T -- Gough, Laura -- Shaver, Gaius R -- Schimel, Joshua P -- England -- Nature. 2013 May 30;497(7451):615-8. doi: 10.1038/nature12129. Epub 2013 May 15.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Ecology, Evolution and Marine Biology, University of California Santa Barbara, Santa Barbara, California 93108, USA. sistla@lifesci.ucsb.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23676669" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Arctic Regions ; Biomass ; Carbon/*analysis ; *Carbon Cycle ; *Cold Climate ; Discriminant Analysis ; *Ecosystem ; Food Chain ; Global Warming/*statistics & numerical data ; History, 20th Century ; History, 21st Century ; Nitrogen/metabolism ; Photosynthesis ; Plants/metabolism ; Rain ; Soil/analysis/*chemistry/parasitology ; Soil Microbiology ; *Temperature ; Time Factors ; Uncertainty
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    Femtosecond switching of magnetism via strongly correlated spin-charge quantum excitations (2013)
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    Publication Date: 2013-04-05
    Description: The technological demand to push the gigahertz (10(9) hertz) switching speed limit of today's magnetic memory and logic devices into the terahertz (10(12) hertz) regime underlies the entire field of spin-electronics and integrated multi-functional devices. This challenge is met by all-optical magnetic switching based on coherent spin manipulation. By analogy to femtosecond chemistry and photosynthetic dynamics--in which photoproducts of chemical and biochemical reactions can be influenced by creating suitable superpositions of molecular states--femtosecond-laser-excited coherence between electronic states can switch magnetic order by 'suddenly' breaking the delicate balance between competing phases of correlated materials: for example, manganites exhibiting colossal magneto-resistance suitable for applications. Here we show femtosecond (10(-15) seconds) photo-induced switching from antiferromagnetic to ferromagnetic ordering in Pr0.7Ca0.3MnO3, by observing the establishment (within about 120 femtoseconds) of a huge temperature-dependent magnetization with photo-excitation threshold behaviour absent in the optical reflectivity. The development of ferromagnetic correlations during the femtosecond laser pulse reveals an initial quantum coherent regime of magnetism, distinguished from the picosecond (10(-12) seconds) lattice-heating regime characterized by phase separation without threshold behaviour. Our simulations reproduce the nonlinear femtosecond spin generation and underpin fast quantum spin-flip fluctuations correlated with coherent superpositions of electronic states to initiate local ferromagnetic correlations. These results merge two fields, femtosecond magnetism in metals and band insulators, and non-equilibrium phase transitions of strongly correlated electrons, in which local interactions exceeding the kinetic energy produce a complex balance of competing orders.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Li, Tianqi -- Patz, Aaron -- Mouchliadis, Leonidas -- Yan, Jiaqiang -- Lograsso, Thomas A -- Perakis, Ilias E -- Wang, Jigang -- England -- Nature. 2013 Apr 4;496(7443):69-73. doi: 10.1038/nature11934.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23552945" target="_blank"〉PubMed〈/a〉
    Keywords: Biology ; Chemistry ; Circular Dichroism ; Electronics ; Iron/chemistry ; *Magnetic Phenomena ; Magnetics ; Optics and Photonics ; Photosynthesis ; *Quantum Theory ; Temperature ; Time Factors
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    Energy: Fuelling the future (2013)
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    Publication Date: 2013-10-18
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉England -- Nature. 2013 Oct 17;502(7471):S60-1. doi: 10.1038/502S60a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24132337" target="_blank"〉PubMed〈/a〉
    Keywords: Biofuels/adverse effects/economics ; Biomass ; Climate Change/statistics & numerical data ; Photosynthesis ; *Renewable Energy/economics ; Solar Energy/economics ; Technology/economics/*trends
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    Sensitivity of tropical carbon to climate change constrained by carbon dioxide variability (2013)
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    Publication Date: 2013-02-08
    Description: The release of carbon from tropical forests may exacerbate future climate change, but the magnitude of the effect in climate models remains uncertain. Coupled climate-carbon-cycle models generally agree that carbon storage on land will increase as a result of the simultaneous enhancement of plant photosynthesis and water use efficiency under higher atmospheric CO(2) concentrations, but will decrease owing to higher soil and plant respiration rates associated with warming temperatures. At present, the balance between these effects varies markedly among coupled climate-carbon-cycle models, leading to a range of 330 gigatonnes in the projected change in the amount of carbon stored on tropical land by 2100. Explanations for this large uncertainty include differences in the predicted change in rainfall in Amazonia and variations in the responses of alternative vegetation models to warming. Here we identify an emergent linear relationship, across an ensemble of models, between the sensitivity of tropical land carbon storage to warming and the sensitivity of the annual growth rate of atmospheric CO(2) to tropical temperature anomalies. Combined with contemporary observations of atmospheric CO(2) concentration and tropical temperature, this relationship provides a tight constraint on the sensitivity of tropical land carbon to climate change. We estimate that over tropical land from latitude 30 degrees north to 30 degrees south, warming alone will release 53 +/- 17 gigatonnes of carbon per kelvin. Compared with the unconstrained ensemble of climate-carbon-cycle projections, this indicates a much lower risk of Amazon forest dieback under CO(2)-induced climate change if CO(2) fertilization effects are as large as suggested by current models. Our study, however, also implies greater certainty that carbon will be lost from tropical land if warming arises from reductions in aerosols or increases in other greenhouse gases.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Cox, Peter M -- Pearson, David -- Booth, Ben B -- Friedlingstein, Pierre -- Huntingford, Chris -- Jones, Chris D -- Luke, Catherine M -- England -- Nature. 2013 Feb 21;494(7437):341-4. doi: 10.1038/nature11882. Epub 2013 Feb 6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉College of Engineering, Mathematics and Physical Science, University of Exeter, Exeter EX4 4QF, UK. p.m.cox@exeter.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23389447" target="_blank"〉PubMed〈/a〉
    Keywords: Carbon Cycle/*physiology ; Carbon Dioxide/analysis/*metabolism ; Cell Respiration ; *Climate Change ; *Models, Theoretical ; Photosynthesis ; Rain ; Temperature ; Trees/*metabolism ; *Tropical Climate ; Uncertainty
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    Late Miocene threshold response of marine algae to carbon dioxide limitation (2013)
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    Publication Date: 2013-08-30
    Description: Coccolithophores are marine algae that use carbon for calcification and photosynthesis. The long-term adaptation of these and other marine algae to decreasing carbon dioxide levels during the Cenozoic era has resulted in modern algae capable of actively enhancing carbon dioxide at the site of photosynthesis. This enhancement occurs through the transport of dissolved bicarbonate (HCO3(-)) and with the help of enzymes whose expression can be modulated by variable aqueous carbon dioxide concentration, [CO2], in laboratory cultures. Coccolithophores preserve the geological history of this adaptation because the stable carbon and oxygen isotopic compositions of their calcite plates (coccoliths), which are preserved in the fossil record, are sensitive to active carbon uptake and transport by the cell. Here we use a model of cellular carbon fluxes and show that at low [CO2] the increased demand for HCO3(-) at the site of photosynthesis results in a diminished allocation of HCO3(-) to calcification, which is most pronounced in larger cells. This results in a large divergence between the carbon isotopic compositions of small versus large coccoliths only at low [CO2]. Our evaluation of the oxygen and carbon isotope record of size-separated fossil coccoliths reveals that this isotopic divergence first arose during the late Miocene to the earliest Pliocene epoch (about 7-5 million years ago). We interpret this to be a threshold response of the cells' carbon acquisition strategies to decreasing [CO2]. The documented coccolithophore response is synchronous with a global shift in terrestrial vegetation distribution between 8 and 5 Myr ago, which has been interpreted by some studies as a floral response to decreasing partial pressures of carbon dioxide () in the atmosphere. We infer a global decrease in carbon dioxide levels for this time interval that has not yet been identified in the sparse proxy record but is synchronous with global cooling and progressive glaciations.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bolton, Clara T -- Stoll, Heather M -- England -- Nature. 2013 Aug 29;500(7464):558-62. doi: 10.1038/nature12448.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Geology Department, University of Oviedo, Jesus Arias de Velasco S/N, 33005, Oviedo, Asturias, Spain. cbolton@geol.uniovi.es〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23985873" target="_blank"〉PubMed〈/a〉
    Keywords: Aquatic Organisms/*metabolism ; Atmosphere/chemistry ; Bicarbonates/metabolism ; Calcification, Physiologic ; Calcium Carbonate/chemistry/metabolism ; Carbon/metabolism ; Carbon Dioxide/analysis/*metabolism ; Carbon Isotopes ; Chloroplasts/metabolism ; Climate ; Fossils ; History, Ancient ; Oxygen Isotopes ; Partial Pressure ; Photosynthesis ; Phytoplankton/*metabolism ; Temperature
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    DMSP biosynthesis by an animal and its role in coral thermal stress response (2013)
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    Publication Date: 2013-10-25
    Description: Globally, reef-building corals are the most prolific producers of dimethylsulphoniopropionate (DMSP), a central molecule in the marine sulphur cycle and precursor of the climate-active gas dimethylsulphide. At present, DMSP production by corals is attributed entirely to their algal endosymbiont, Symbiodinium. Combining chemical, genomic and molecular approaches, we show that coral juveniles produce DMSP in the absence of algal symbionts. DMSP levels increased up to 54% over time in newly settled coral juveniles lacking algal endosymbionts, and further increases, up to 76%, were recorded when juveniles were subjected to thermal stress. We uncovered coral orthologues of two algal genes recently identified in DMSP biosynthesis, strongly indicating that corals possess the enzymatic machinery necessary for DMSP production. Our results overturn the paradigm that photosynthetic organisms are the sole biological source of DMSP, and highlight the double jeopardy represented by worldwide declining coral cover, as the potential to alleviate thermal stress through coral-produced DMSP declines correspondingly.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Raina, Jean-Baptiste -- Tapiolas, Dianne M -- Foret, Sylvain -- Lutz, Adrian -- Abrego, David -- Ceh, Janja -- Seneca, Francois O -- Clode, Peta L -- Bourne, David G -- Willis, Bette L -- Motti, Cherie A -- England -- Nature. 2013 Oct 31;502(7473):677-80. doi: 10.1038/nature12677. Epub 2013 Oct 23.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉1] AIMS@JCU, and School of Marine and Tropical Biology, James Cook University, Townsville, Queensland 4811, Australia [2] Australian Institute of Marine Science, PMB3, Townsville MC, Townsville, Queensland 4810, Australia [3] ARC Centre of Excellence for Coral Reef Studies, School of Marine and Tropical Biology, James Cook University, Townsville, Queensland 4811, Australia.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24153189" target="_blank"〉PubMed〈/a〉
    Keywords: Acrylates/analysis/metabolism ; Algal Proteins/genetics ; Animals ; Anthozoa/genetics/metabolism/*physiology ; Climate Change ; Photosynthesis ; Secondary Metabolism ; *Stress, Physiological ; Sulfonium Compounds/*metabolism ; Symbiosis ; *Temperature ; Time Factors
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    Glucose-TOR signalling reprograms the transcriptome and activates meristems (2013)
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    Publication Date: 2013-04-02
    Description: Meristems encompass stem/progenitor cells that sustain postembryonic growth of all plant organs. How meristems are activated and sustained by nutrient signalling remains enigmatic in photosynthetic plants. Combining chemical manipulations and chemical genetics at the photoautotrophic transition checkpoint, we reveal that shoot photosynthesis-derived glucose drives target-of-rapamycin (TOR) signalling relays through glycolysis and mitochondrial bioenergetics to control root meristem activation, which is decoupled from direct glucose sensing, growth-hormone signalling and stem-cell maintenance. Surprisingly, glucose-TOR signalling dictates transcriptional reprogramming of remarkable gene sets involved in central and secondary metabolism, cell cycle, transcription, signalling, transport and protein folding. Systems, cellular and genetic analyses uncover TOR phosphorylation of E2Fa transcription factor for an unconventional activation of S-phase genes, and glucose-signalling defects in e2fa root meristems. Our findings establish pivotal roles of glucose-TOR signalling in unprecedented transcriptional networks wiring central metabolism and biosynthesis for energy and biomass production, and integrating localized stem/progenitor-cell proliferation through inter-organ nutrient coordination to control developmental transition and growth.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4140196/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4140196/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Xiong, Yan -- McCormack, Matthew -- Li, Lei -- Hall, Qi -- Xiang, Chengbin -- Sheen, Jen -- R01 GM060493/GM/NIGMS NIH HHS/ -- R01 GM070567/GM/NIGMS NIH HHS/ -- England -- Nature. 2013 Apr 11;496(7444):181-6. doi: 10.1038/nature12030. Epub 2013 Mar 31.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Molecular Biology and Centre for Computational and Integrative Biology, Massachusetts General Hospital, and Department of Genetics, Harvard Medical School, Boston, Massachusetts 02114, USA. xiong@molbio.mgh.harvard.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23542588" target="_blank"〉PubMed〈/a〉
    Keywords: Arabidopsis/*genetics/growth & development/*metabolism ; Arabidopsis Proteins/*metabolism ; Cytokinins/metabolism ; E2F Transcription Factors/metabolism ; Enzyme Activation ; *Gene Expression Regulation, Plant ; Gene Regulatory Networks/genetics ; Glucose/*metabolism ; Indoleacetic Acids/metabolism ; Meristem/genetics/growth & development/*metabolism ; Phosphatidylinositol 3-Kinases/*metabolism ; Phosphorylation ; Photosynthesis ; S Phase/genetics ; *Signal Transduction ; Transcription, Genetic/genetics ; Transcriptional Activation ; *Transcriptome/genetics
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    Wild weather can send greenhouse gases spiralling (2013)
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    Publication Date: 2013-04-13
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Schiermeier, Quirin -- England -- Nature. 2013 Apr 11;496(7444):147. doi: 10.1038/496147a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23579654" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere ; *Carbon Cycle ; Carbon Dioxide/*analysis/metabolism ; Carbon Sequestration ; Cell Respiration ; Congresses as Topic ; Droughts/statistics & numerical data ; Extreme Heat ; Feedback ; Greenhouse Effect/*statistics & numerical data ; Models, Theoretical ; Photosynthesis ; Plants/metabolism ; Soil Microbiology ; Water/metabolism ; *Weather
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    Atmospheric oxygenation three billion years ago (2013)
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    Publication Date: 2013-09-27
    Description: It is widely assumed that atmospheric oxygen concentrations remained persistently low (less than 10(-5) times present levels) for about the first 2 billion years of Earth's history. The first long-term oxygenation of the atmosphere is thought to have taken place around 2.3 billion years ago, during the Great Oxidation Event. Geochemical indications of transient atmospheric oxygenation, however, date back to 2.6-2.7 billion years ago. Here we examine the distribution of chromium isotopes and redox-sensitive metals in the approximately 3-billion-year-old Nsuze palaeosol and in the near-contemporaneous Ijzermyn iron formation from the Pongola Supergroup, South Africa. We find extensive mobilization of redox-sensitive elements through oxidative weathering. Furthermore, using our data we compute a best minimum estimate for atmospheric oxygen concentrations at that time of 3 x 10(-4) times present levels. Overall, our findings suggest that there were appreciable levels of atmospheric oxygen about 3 billion years ago, more than 600 million years before the Great Oxidation Event and some 300-400 million years earlier than previous indications for Earth surface oxygenation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Crowe, Sean A -- Dossing, Lasse N -- Beukes, Nicolas J -- Bau, Michael -- Kruger, Stephanus J -- Frei, Robert -- Canfield, Donald E -- England -- Nature. 2013 Sep 26;501(7468):535-8. doi: 10.1038/nature12426.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institute of Biology, University of Southern Denmark, Odense 5230, Denmark. sean.crowe@ubc.ca〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24067713" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere/*chemistry ; Biological Evolution ; Chromium Isotopes/analysis ; Cyanobacteria/metabolism ; Earth (Planet) ; Geologic Sediments/analysis/chemistry ; History, Ancient ; Iron/analysis ; Oxidation-Reduction ; Oxygen/*analysis/metabolism ; Photosynthesis ; South Africa
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    Terrestrial water fluxes dominated by transpiration (2013)
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    Publication Date: 2013-04-05
    Description: Renewable fresh water over continents has input from precipitation and losses to the atmosphere through evaporation and transpiration. Global-scale estimates of transpiration from climate models are poorly constrained owing to large uncertainties in stomatal conductance and the lack of catchment-scale measurements required for model calibration, resulting in a range of predictions spanning 20 to 65 per cent of total terrestrial evapotranspiration (14,000 to 41,000 km(3) per year) (refs 1, 2, 3, 4, 5). Here we use the distinct isotope effects of transpiration and evaporation to show that transpiration is by far the largest water flux from Earth's continents, representing 80 to 90 per cent of terrestrial evapotranspiration. On the basis of our analysis of a global data set of large lakes and rivers, we conclude that transpiration recycles 62,000 +/- 8,000 km(3) of water per year to the atmosphere, using half of all solar energy absorbed by land surfaces in the process. We also calculate CO2 uptake by terrestrial vegetation by connecting transpiration losses to carbon assimilation using water-use efficiency ratios of plants, and show the global gross primary productivity to be 129 +/- 32 gigatonnes of carbon per year, which agrees, within the uncertainty, with previous estimates. The dominance of transpiration water fluxes in continental evapotranspiration suggests that, from the point of view of water resource forecasting, climate model development should prioritize improvements in simulations of biological fluxes rather than physical (evaporation) fluxes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Jasechko, Scott -- Sharp, Zachary D -- Gibson, John J -- Birks, S Jean -- Yi, Yi -- Fawcett, Peter J -- England -- Nature. 2013 Apr 18;496(7445):347-50. doi: 10.1038/nature11983. Epub 2013 Apr 3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA. jasechko@unm.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23552893" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere/chemistry ; Carbon Dioxide/analysis/metabolism ; Ecosystem ; Fresh Water/*analysis/chemistry ; Lakes ; Oceans and Seas ; Photosynthesis ; Plant Transpiration/*physiology ; Plants/*metabolism ; Rain ; Rivers ; Uncertainty ; Volatilization ; *Water Movements
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    Dynamics of a Snowball Earth ocean (2013)
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    Publication Date: 2013-03-08
    Description: Geological evidence suggests that marine ice extended to the Equator at least twice during the Neoproterozoic era (about 750 to 635 million years ago), inspiring the Snowball Earth hypothesis that the Earth was globally ice-covered. In a possible Snowball Earth climate, ocean circulation and mixing processes would have set the melting and freezing rates that determine ice thickness, would have influenced the survival of photosynthetic life, and may provide important constraints for the interpretation of geochemical and sedimentological observations. Here we show that in a Snowball Earth, the ocean would have been well mixed and characterized by a dynamic circulation, with vigorous equatorial meridional overturning circulation, zonal equatorial jets, a well developed eddy field, strong coastal upwelling and convective mixing. This is in contrast to the sluggish ocean often expected in a Snowball Earth scenario owing to the insulation of the ocean from atmospheric forcing by the thick ice cover. As a result of vigorous convective mixing, the ocean temperature, salinity and density were either uniform in the vertical direction or weakly stratified in a few locations. Our results are based on a model that couples ice flow and ocean circulation, and is driven by a weak geothermal heat flux under a global ice cover about a kilometre thick. Compared with the modern ocean, the Snowball Earth ocean had far larger vertical mixing rates, and comparable horizontal mixing by ocean eddies. The strong circulation and coastal upwelling resulted in melting rates near continents as much as ten times larger than previously estimated. Although we cannot resolve the debate over the existence of global ice cover, we discuss the implications for the nutrient supply of photosynthetic activity and for banded iron formations. Our insights and constraints on ocean dynamics may help resolve the Snowball Earth controversy when combined with future geochemical and geological observations.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Ashkenazy, Yosef -- Gildor, Hezi -- Losch, Martin -- Macdonald, Francis A -- Schrag, Daniel P -- Tziperman, Eli -- England -- Nature. 2013 Mar 7;495(7439):90-3. doi: 10.1038/nature11894.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Solar Energy and Environmental Physics, The Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Midreshet Ben-Gurion, 84990, Israel. ashkena@bgu.ac.il〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23467167" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere ; *Earth (Planet) ; History, Ancient ; *Ice Cover ; Models, Theoretical ; Oceans and Seas ; Photosynthesis ; Salinity ; *Seawater/analysis/chemistry ; *Snow ; Temperature ; *Water Movements
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    Q&A: A slow-motion crisis. Interview by Michael Eisenstein (2012)
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    Publication Date: 2012-03-02
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Falkowski, Paul -- England -- Nature. 2012 Feb 29;483(7387):S21. doi: 10.1038/483S21a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22378124" target="_blank"〉PubMed〈/a〉
    Keywords: Aquatic Organisms/*metabolism ; Environmental Restoration and Remediation ; Eutrophication ; Extinction, Biological ; *Global Warming ; *Human Activities ; Interdisciplinary Studies ; Marine Biology ; Photosynthesis ; Phytoplankton/*metabolism ; Seawater/chemistry/microbiology ; Time Factors
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    Extended leaf phenology and the autumn niche in deciduous forest invasions (2012)
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    Publication Date: 2012-04-27
    Description: The phenology of growth in temperate deciduous forests, including the timing of leaf emergence and senescence, has strong control over ecosystem properties such as productivity and nutrient cycling, and has an important role in the carbon economy of understory plants. Extended leaf phenology, whereby understory species assimilate carbon in early spring before canopy closure or in late autumn after canopy fall, has been identified as a key feature of many forest species invasions, but it remains unclear whether there are systematic differences in the growth phenology of native and invasive forest species or whether invaders are more responsive to warming trends that have lengthened the duration of spring or autumn growth. Here, in a 3-year monitoring study of 43 native and 30 non-native shrub and liana species common to deciduous forests in the eastern United States, I show that extended autumn leaf phenology is a common attribute of eastern US forest invasions, where non-native species are extending the autumn growing season by an average of 4 weeks compared with natives. In contrast, there was no consistent evidence that non-natives as a group show earlier spring growth phenology, and non-natives were not better able to track interannual variation in spring temperatures. Seasonal leaf production and photosynthetic data suggest that most non-native species capture a significant proportion of their annual carbon assimilate after canopy leaf fall, a behaviour that was virtually absent in natives and consistent across five phylogenetic groups. Pronounced differences in how native and non-native understory species use pre- and post-canopy environments suggest eastern US invaders are driving a seasonal redistribution of forest productivity that may rival climate change in its impact on forest processes.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Fridley, Jason D -- England -- Nature. 2012 May 17;485(7398):359-62. doi: 10.1038/nature11056.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Biology, Syracuse University, 107 College Place, Syracuse, New York 13244, USA. fridley@syr.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22535249" target="_blank"〉PubMed〈/a〉
    Keywords: Carbon/metabolism ; *Ecosystem ; *Introduced Species ; Photosynthesis ; Plant Leaves/classification/*growth & development ; *Seasons ; Temperature ; Time Factors ; Trees/classification/*growth & development ; United States
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    Endospore abundance, microbial growth and necromass turnover in deep sub-seafloor sediment (2012)
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    Publication Date: 2012-03-20
    Description: Two decades of scientific ocean drilling have demonstrated widespread microbial life in deep sub-seafloor sediment, and surprisingly high microbial-cell numbers. Despite the ubiquity of life in the deep biosphere, the large community sizes and the low energy fluxes in this vast buried ecosystem are not yet understood. It is not known whether organisms of the deep biosphere are specifically adapted to extremely low energy fluxes or whether most of the observed cells are in a dormant, spore-like state. Here we apply a new approach--the D:L-amino-acid model--to quantify the distributions and turnover times of living microbial biomass, endospores and microbial necromass, as well as to determine their role in the sub-seafloor carbon budget. The approach combines sensitive analyses of unique bacterial markers (muramic acid and D-amino acids) and the bacterial endospore marker, dipicolinic acid, with racemization dynamics of stereo-isomeric amino acids. Endospores are as abundant as vegetative cells and microbial activity is extremely low, leading to microbial biomass turnover times of hundreds to thousands of years. We infer from model calculations that biomass production is sustained by organic carbon deposited from the surface photosynthetic world millions of years ago and that microbial necromass is recycled over timescales of hundreds of thousands of years.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lomstein, Bente Aa -- Langerhuus, Alice T -- D'Hondt, Steven -- Jorgensen, Bo B -- Spivack, Arthur J -- England -- Nature. 2012 Mar 18;484(7392):101-4. doi: 10.1038/nature10905.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Bioscience, Section for Microbiology, Aarhus University, Building 1540, Ny Munkegade 114, DK-8000 Aarhus C, Denmark. bente.lomstein@biology.au.dk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22425999" target="_blank"〉PubMed〈/a〉
    Keywords: Altitude ; Amino Acids/analysis/chemistry/metabolism ; Aquatic Organisms/chemistry/growth & development/*isolation & purification ; Archaea/chemistry/cytology/*growth & development/isolation & purification ; Bacteria/chemistry/cytology/*growth & development/isolation & purification ; Biomarkers/analysis ; *Biomass ; Carbon/metabolism ; Cell Wall/chemistry ; Geologic Sediments/*microbiology ; Muramic Acids/analysis ; Oceans and Seas ; Oxidation-Reduction ; Peru ; Photosynthesis ; Picolinic Acids/analysis ; Seawater/*microbiology ; Spores, Bacterial/chemistry/growth & development/isolation & purification ; Time Factors
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    Persistent near-tropical warmth on the Antarctic continent during the early Eocene epoch (2012)
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    Publication Date: 2012-08-04
    Description: The warmest global climates of the past 65 million years occurred during the early Eocene epoch (about 55 to 48 million years ago), when the Equator-to-pole temperature gradients were much smaller than today and atmospheric carbon dioxide levels were in excess of one thousand parts per million by volume. Recently the early Eocene has received considerable interest because it may provide insight into the response of Earth's climate and biosphere to the high atmospheric carbon dioxide levels that are expected in the near future as a consequence of unabated anthropogenic carbon emissions. Climatic conditions of the early Eocene 'greenhouse world', however, are poorly constrained in critical regions, particularly Antarctica. Here we present a well-dated record of early Eocene climate on Antarctica from an ocean sediment core recovered off the Wilkes Land coast of East Antarctica. The information from biotic climate proxies (pollen and spores) and independent organic geochemical climate proxies (indices based on branched tetraether lipids) yields quantitative, seasonal temperature reconstructions for the early Eocene greenhouse world on Antarctica. We show that the climate in lowland settings along the Wilkes Land coast (at a palaeolatitude of about 70 degrees south) supported the growth of highly diverse, near-tropical forests characterized by mesothermal to megathermal floral elements including palms and Bombacoideae. Notably, winters were extremely mild (warmer than 10 degrees C) and essentially frost-free despite polar darkness, which provides a critical new constraint for the validation of climate models and for understanding the response of high-latitude terrestrial ecosystems to increased carbon dioxide forcing.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pross, Jorg -- Contreras, Lineth -- Bijl, Peter K -- Greenwood, David R -- Bohaty, Steven M -- Schouten, Stefan -- Bendle, James A -- Rohl, Ursula -- Tauxe, Lisa -- Raine, J Ian -- Huck, Claire E -- van de Flierdt, Tina -- Jamieson, Stewart S R -- Stickley, Catherine E -- van de Schootbrugge, Bas -- Escutia, Carlota -- Brinkhuis, Henk -- Integrated Ocean Drilling Program Expedition 318 Scientists -- England -- Nature. 2012 Aug 2;488(7409):73-7. doi: 10.1038/nature11300.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Paleoenvironmental Dynamics Group, Institute of Geosciences, Goethe University Frankfurt, Altenhoferallee 1, 60438 Frankfurt, Germany. joerg.pross@em.uni-frankfurt.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22859204" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Antarctic Regions ; Atmosphere/chemistry ; Carbon Dioxide/analysis ; Cell Respiration ; Ecosystem ; Geologic Sediments/chemistry ; Greenhouse Effect/*history ; History, Ancient ; Human Activities ; Lipids/analysis ; Models, Theoretical ; Photosynthesis ; Pollen ; Reproducibility of Results ; Seasons ; Spores/isolation & purification ; *Temperature ; Trees/growth & development ; *Tropical Climate
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    Reconciling the temperature dependence of respiration across timescales and ecosystem types (2012)
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    Publication Date: 2012-06-23
    Description: Ecosystem respiration is the biotic conversion of organic carbon to carbon dioxide by all of the organisms in an ecosystem, including both consumers and primary producers. Respiration exhibits an exponential temperature dependence at the subcellular and individual levels, but at the ecosystem level respiration can be modified by many variables including community abundance and biomass, which vary substantially among ecosystems. Despite its importance for predicting the responses of the biosphere to climate change, it is as yet unknown whether the temperature dependence of ecosystem respiration varies systematically between aquatic and terrestrial environments. Here we use the largest database of respiratory measurements yet compiled to show that the sensitivity of ecosystem respiration to seasonal changes in temperature is remarkably similar for diverse environments encompassing lakes, rivers, estuaries, the open ocean and forested and non-forested terrestrial ecosystems, with an average activation energy similar to that of the respiratory complex (approximately 0.65 electronvolts (eV)). By contrast, annual ecosystem respiration shows a substantially greater temperature dependence across aquatic (approximately 0.65 eV) versus terrestrial ecosystems (approximately 0.32 eV) that span broad geographic gradients in temperature. Using a model derived from metabolic theory, these findings can be reconciled by similarities in the biochemical kinetics of metabolism at the subcellular level, and fundamental differences in the importance of other variables besides temperature-such as primary productivity and allochthonous carbon inputs-on the structure of aquatic and terrestrial biota at the community level.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Yvon-Durocher, Gabriel -- Caffrey, Jane M -- Cescatti, Alessandro -- Dossena, Matteo -- del Giorgio, Paul -- Gasol, Josep M -- Montoya, Jose M -- Pumpanen, Jukka -- Staehr, Peter A -- Trimmer, Mark -- Woodward, Guy -- Allen, Andrew P -- England -- Nature. 2012 Jul 26;487(7408):472-6. doi: 10.1038/nature11205.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉School of Biological & Chemical Sciences, Queen Mary University of London, London E1 4NS, UK. g.yvon-durocher@exeter.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22722862" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Biomass ; Biota ; Carbon/*metabolism ; Carbon Dioxide/*metabolism ; Cell Respiration ; Data Collection ; *Ecosystem ; *Global Warming ; Humans ; Kinetics ; Lakes ; Marine Biology ; *Oxygen Consumption ; Photosynthesis ; Rivers ; Seasons ; Seawater ; *Temperature ; Time Factors ; Trees/metabolism
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    Oceanography: Forecasting the rain ratio (2011)
    Nature Publishing Group (NPG)
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    Publication Date: 2011-08-05
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hutchins, David A -- England -- Nature. 2011 Aug 3;476(7358):41-2. doi: 10.1038/476041a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21814273" target="_blank"〉PubMed〈/a〉
    Keywords: Aquatic Organisms/chemistry/metabolism ; Atmosphere/chemistry ; *Calcification, Physiologic ; Calcium Carbonate/*analysis/chemistry/metabolism ; Carbon Cycle ; Carbon Dioxide/*analysis/chemistry ; Carbonic Acid/*analysis/chemistry ; Fossils ; Hydrogen-Ion Concentration ; Oceans and Seas ; Photosynthesis ; Phytoplankton/chemistry/*metabolism ; *Rain ; Seawater/*chemistry
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    Sensitivity of coccolithophores to carbonate chemistry and ocean acidification (2011)
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    Publication Date: 2011-08-05
    Description: About one-third of the carbon dioxide (CO(2)) released into the atmosphere as a result of human activity has been absorbed by the oceans, where it partitions into the constituent ions of carbonic acid. This leads to ocean acidification, one of the major threats to marine ecosystems and particularly to calcifying organisms such as corals, foraminifera and coccolithophores. Coccolithophores are abundant phytoplankton that are responsible for a large part of modern oceanic carbonate production. Culture experiments investigating the physiological response of coccolithophore calcification to increased CO(2) have yielded contradictory results between and even within species. Here we quantified the calcite mass of dominant coccolithophores in the present ocean and over the past forty thousand years, and found a marked pattern of decreasing calcification with increasing partial pressure of CO(2) and concomitant decreasing concentrations of CO(3)(2-). Our analyses revealed that differentially calcified species and morphotypes are distributed in the ocean according to carbonate chemistry. A substantial impact on the marine carbon cycle might be expected upon extrapolation of this correlation to predicted ocean acidification in the future. However, our discovery of a heavily calcified Emiliania huxleyi morphotype in modern waters with low pH highlights the complexity of assemblage-level responses to environmental forcing factors.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Beaufort, L -- Probert, I -- de Garidel-Thoron, T -- Bendif, E M -- Ruiz-Pino, D -- Metzl, N -- Goyet, C -- Buchet, N -- Coupel, P -- Grelaud, M -- Rost, B -- Rickaby, R E M -- de Vargas, C -- 205150/European Research Council/International -- England -- Nature. 2011 Aug 3;476(7358):80-3. doi: 10.1038/nature10295.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉CEREGE, CNRS/Universite Aix-Marseille, Avenue L. Philibert BP80, 13545 Aix-en-Provence, Cedex 4, France. beaufort@cerege.fr〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21814280" target="_blank"〉PubMed〈/a〉
    Keywords: Aquatic Organisms/chemistry/metabolism ; Atmosphere/chemistry ; Body Weight ; *Calcification, Physiologic ; Calcium/metabolism ; Calcium Carbonate/*analysis/chemistry/metabolism ; Carbon Cycle ; Carbon Dioxide/analysis/chemistry ; Carbonic Acid/*analysis/chemistry ; Fossils ; Geologic Sediments/chemistry ; Haptophyta/chemistry/*metabolism ; Hydrogen-Ion Concentration ; Molecular Sequence Data ; Oceans and Seas ; Pacific Ocean ; Partial Pressure ; Photosynthesis ; Phytoplankton/chemistry/*metabolism ; Seawater/*chemistry
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    What lies ahead (2011)
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    Publication Date: 2011-01-07
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉England -- Nature. 2011 Jan 6;469(7328):23-5. doi: 10.1038/469023a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21209640" target="_blank"〉PubMed〈/a〉
    Keywords: Biomimetics/trends ; Biopolymers/chemistry ; Chemistry/methods/*trends ; Conservation of Energy Resources/trends ; Drug Design ; Ecology/trends ; Global Warming ; Green Chemistry Technology/trends ; Molecular Biology/trends ; Nanotechnology/trends ; Photosynthesis ; Research Personnel ; Solar Energy ; Stereoisomerism ; Thermodynamics
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    Forum. Chemical engineering: Fuel for debate (2011)
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    Publication Date: 2011-08-26
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mayfield, Stephen -- Wong, P K -- England -- Nature. 2011 Aug 24;476(7361):402-3. doi: 10.1038/476402a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21866147" target="_blank"〉PubMed〈/a〉
    Keywords: *Biocatalysis ; Biochemical Processes ; Bioengineering/*methods ; Biofuels/*supply & distribution ; Biomass ; *Catalysis ; Chemical Engineering/*methods ; Conservation of Energy Resources/*methods ; Lignin/chemistry/metabolism ; Photosynthesis ; Saccharum/chemistry/metabolism ; Temperature ; Zea mays/chemistry/metabolism
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    Early oxygenation of the terrestrial environment during the Mesoproterozoic (2010)
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    Publication Date: 2010-11-12
    Description: Geochemical data from ancient sedimentary successions provide evidence for the progressive evolution of Earth's atmosphere and oceans. Key stages in increasing oxygenation are postulated for the Palaeoproterozoic era ( approximately 2.3 billion years ago, Gyr ago) and the late Proterozoic eon (about 0.8 Gyr ago), with the latter implicated in the subsequent metazoan evolutionary expansion. In support of this rise in oxygen concentrations, a large database shows a marked change in the bacterially mediated fractionation of seawater sulphate to sulphide of Delta(34)S 〈 25 per thousand before 1 Gyr to 〉/=50 per thousand after 0.64 Gyr. This change in Delta(34)S has been interpreted to represent the evolution from single-step bacterial sulphate reduction to a combination of bacterial sulphate reduction and sulphide oxidation, largely bacterially mediated. This evolution is seen as marking the rise in atmospheric oxygen concentrations and the evolution of non-photosynthetic sulphide-oxidizing bacteria. Here we report Delta(34)S values exceeding 50 per thousand from a terrestrial Mesoproterozoic (1.18 Gyr old) succession in Scotland, a time period that is at present poorly characterized. This level of fractionation implies disproportionation in the sulphur cycle, probably involving sulphide-oxidizing bacteria, that is not evident from Delta(34)S data in the marine record. Disproportionation in both red beds and lacustrine black shales at our study site suggests that the Mesoproterozoic terrestrial environment was sufficiently oxygenated to support a biota that was adapted to an oxygen-rich atmosphere, but had also penetrated into subsurface sediment.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Parnell, John -- Boyce, Adrian J -- Mark, Darren -- Bowden, Stephen -- Spinks, Sam -- England -- Nature. 2010 Nov 11;468(7321):290-3. doi: 10.1038/nature09538.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉School of Geosciences, University of Aberdeen, Aberdeen AB24 3UE, UK. j.parnell@abdn.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21068840" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere/chemistry ; Bacteria/metabolism ; Geologic Sediments/*chemistry/microbiology ; History, Ancient ; Iron/analysis/chemistry ; Oxidation-Reduction ; Oxygen/analysis/*metabolism ; Photosynthesis ; Scotland ; Seawater/chemistry ; Sulfates/metabolism ; Sulfides/analysis/chemistry/metabolism
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    Quantum physics: Hot entanglement (2010)
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    Publication Date: 2010-12-15
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Vedral, Vlatko -- England -- Nature. 2010 Dec 9;468(7325):769-70. doi: 10.1038/468769a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/21150986" target="_blank"〉PubMed〈/a〉
    Keywords: Hot Temperature ; Models, Biological ; Photosynthesis ; *Quantum Theory ; *Thermodynamics
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    Salamander's egg surprise (2010)
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    Publication Date: 2010-08-06
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Petherick, Anna -- England -- Nature. 2010 Aug 5;466(7307):675. doi: 10.1038/466675a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/20686543" target="_blank"〉PubMed〈/a〉
    Keywords: Ambystoma/*embryology ; Animals ; Chlorophyta/*physiology ; Female ; Oviducts/metabolism ; Ovum/growth & development/*metabolism ; Photosynthesis ; *Symbiosis
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    When Earth greened over (2009)
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    Publication Date: 2009-07-10
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Hand, Eric -- England -- Nature. 2009 Jul 9;460(7252):161. doi: 10.1038/460161a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19587733" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Biological Evolution ; Carbon/metabolism ; Cell Respiration ; *Earth (Planet) ; *Ecosystem ; Fossils ; History, Ancient ; Oceans and Seas ; Oxygen/analysis/*metabolism ; Photosynthesis ; Plants/*metabolism ; Seawater/chemistry
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    Biogeochemistry: Carbonate rocks deconstructed (2009)
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    Publication Date: 2009-08-08
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Arthur, Michael A -- England -- Nature. 2009 Aug 6;460(7256):698-9. doi: 10.1038/460698a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19661908" target="_blank"〉PubMed〈/a〉
    Keywords: Calcium Carbonate/chemistry ; Carbon/chemistry/*metabolism ; Carbon Isotopes ; Carbonates/*analysis/*chemistry ; Earth (Planet) ; Geologic Sediments/*chemistry ; History, Ancient ; Oceans and Seas ; Oxygen/analysis ; Oxygen Isotopes ; Photosynthesis ; Plants/metabolism
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    Arctic ecology: Tundra's burning (2009)
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    Publication Date: 2009-09-04
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Qiu, Jane -- England -- Nature. 2009 Sep 3;461(7260):34-6. doi: 10.1038/461034a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19727180" target="_blank"〉PubMed〈/a〉
    Keywords: Alaska ; Animals ; Arctic Regions ; Atmosphere/chemistry ; Carbon/*analysis/metabolism ; Carbon Dioxide/analysis/metabolism ; *Ecosystem ; *Fires ; Freezing ; Fresh Water/chemistry ; Geologic Sediments/chemistry ; Greenhouse Effect ; Photosynthesis ; Soil/analysis
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    A measure of marine life (2009)
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    Publication Date: 2009-05-16
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉England -- Nature. 2009 May 14;459(7244):140. doi: 10.1038/459140a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19444162" target="_blank"〉PubMed〈/a〉
    Keywords: *Marine Biology/trends ; Photosynthesis ; Prochlorococcus/growth & development/isolation & purification/metabolism ; Time Factors ; *Water Microbiology
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    Net carbon dioxide losses of northern ecosystems in response to autumn warming (2008)
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    Publication Date: 2008-01-04
    Description: The carbon balance of terrestrial ecosystems is particularly sensitive to climatic changes in autumn and spring, with spring and autumn temperatures over northern latitudes having risen by about 1.1 degrees C and 0.8 degrees C, respectively, over the past two decades. A simultaneous greening trend has also been observed, characterized by a longer growing season and greater photosynthetic activity. These observations have led to speculation that spring and autumn warming could enhance carbon sequestration and extend the period of net carbon uptake in the future. Here we analyse interannual variations in atmospheric carbon dioxide concentration data and ecosystem carbon dioxide fluxes. We find that atmospheric records from the past 20 years show a trend towards an earlier autumn-to-winter carbon dioxide build-up, suggesting a shorter net carbon uptake period. This trend cannot be explained by changes in atmospheric transport alone and, together with the ecosystem flux data, suggest increasing carbon losses in autumn. We use a process-based terrestrial biosphere model and satellite vegetation greenness index observations to investigate further the observed seasonal response of northern ecosystems to autumnal warming. We find that both photosynthesis and respiration increase during autumn warming, but the increase in respiration is greater. In contrast, warming increases photosynthesis more than respiration in spring. Our simulations and observations indicate that northern terrestrial ecosystems may currently lose carbon dioxide in response to autumn warming, with a sensitivity of about 0.2 PgC degrees C(-1), offsetting 90% of the increased carbon dioxide uptake during spring. If future autumn warming occurs at a faster rate than in spring, the ability of northern ecosystems to sequester carbon may be diminished earlier than previously suggested.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Piao, Shilong -- Ciais, Philippe -- Friedlingstein, Pierre -- Peylin, Philippe -- Reichstein, Markus -- Luyssaert, Sebastiaan -- Margolis, Hank -- Fang, Jingyun -- Barr, Alan -- Chen, Anping -- Grelle, Achim -- Hollinger, David Y -- Laurila, Tuomas -- Lindroth, Anders -- Richardson, Andrew D -- Vesala, Timo -- England -- Nature. 2008 Jan 3;451(7174):49-52. doi: 10.1038/nature06444.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉LSCE, UMR CEA-CNRS, Batiment 709, CE, L'Orme des Merisiers, F-91191 Gif-sur-Yvette, France. slpiao@lsce.ipsl.fr〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18172494" target="_blank"〉PubMed〈/a〉
    Keywords: Atmosphere/chemistry ; Biomass ; Carbon Dioxide/analysis/*metabolism ; Cell Respiration ; *Ecosystem ; Fossil Fuels ; Geography ; Greenhouse Effect ; History, 20th Century ; History, 21st Century ; Oceans and Seas ; Photosynthesis ; Plant Transpiration ; Plants/metabolism ; Rain ; *Seasons ; Soil/analysis ; *Temperature ; Water/metabolism
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    Evolutionary biology: bridge over troublesome plastids (2008)
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    Publication Date: 2008-02-22
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Keeling, Patrick J -- England -- Nature. 2008 Feb 21;451(7181):896-7. doi: 10.1038/451896a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18288173" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Eukaryota/classification/cytology ; Eukaryotic Cells/*classification/*cytology/metabolism ; Parasites/*classification/*cytology/genetics ; Photosynthesis ; *Phylogeny ; Plasmodium falciparum/classification ; Plastids/*metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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    Catalysis: the art of splitting water (2008)
    Nature Publishing Group (NPG)
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    Publication Date: 2008-02-15
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Meyer, Thomas J -- England -- Nature. 2008 Feb 14;451(7180):778-9. doi: 10.1038/451778a.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18273008" target="_blank"〉PubMed〈/a〉
    Keywords: Catalysis ; Hydrogen/chemistry ; Oxidation-Reduction ; Oxygen/chemistry ; Photosynthesis ; Water/*chemistry
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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    Terrestrial ecosystem carbon dynamics and climate feedbacks (2008)
    Nature Publishing Group (NPG)
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    Publication Date: 2008-01-19
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Heimann, Martin -- Reichstein, Markus -- England -- Nature. 2008 Jan 17;451(7176):289-92. doi: 10.1038/nature06591.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Max Planck Institute for Biogeochemistry, Hans-Knoll-Strasse 10, D-07745 Jena, Germany. martin.heimann@bgc-jena.mpg.de〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18202646" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Carbon/*metabolism ; Carbon Dioxide/metabolism ; Cell Respiration ; *Climate ; *Ecosystem ; *Feedback ; Photosynthesis
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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    Physiological characteristics of Japanese red pine, Pinus densiflora Sieb. et Zucc., in declined forests at Mt. Gokurakuji in Hiroshima Prefecture, Japan (2000)
    Springer
    Trees 14 (2000), S. 305-311 
    Details
    ISSN: 0931-1890
    Keywords: Key words Air pollution ; Ethylene ; Chlorophyll fluorescence ; Photosynthesis ; Pinus densiflora
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The decline of Japanese red pine trees (Pinus densiflora Sieb. et Zucc.) at Mt. Gokurakuji (693 m a.s.l.), 30 km west of Hiroshima city, west Japan, was studied. The effects of air pollution and acid deposition on the physiological characteristics of the trees, especially those of the needles, were investigated. Ozone concentration was not correlated with the physiological status of the needles and SO2 concentration was not high in the declined area. NO2 concentration correlated negatively with needle longevity while it correlated positively with ethylene emission from 1-year-old needles. Average needle longevity was about 2.8 years in non-declined areas; however the longevity was 1.3 years in the most polluted area. The minimal fluorescence at night (F 0)of 1-year-old needles decreased with increasing NO2 concentration. The maximum stomatal conductance (gl), net photosynthesis (P n)and intercellular CO2 concentration (C i) in the declined areas were lower than in the non- declined areas (about 50%, 30% and 20% lower, respectively). The lower C isuggested that the major part of the decrease in P ncan be explained by stomatal restriction. The soil pH, N content and C/N ratio showed no significant difference between the declined and non-declined areas. The physiological disorders of needles were due to the damage by air pollutants, and important roles of NO2 are suggested. Lowering of P n and the shortening of needle longevity appear to be the main causes of the decline in pines in the forest decline area.
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    Monitoring the physiological activity of plants by means of EPR spectroscopy. Mn(II) signals in Pinus nigra Arnold (2000)
    Springer
    Trees 14 (2000), S. 312-315 
    Details
    ISSN: 0931-1890
    Keywords: Key words Electron paramagnetic resonance spectroscopy ; Photosynthesis ; Ageing ; Pinus nigra ; Biosensors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Differently aged needles from a Pinus nigra Arnold tree growing in a typical urban area have been examined by means of electron paramagnetic resonance (EPR) spectroscopy, and the variation of the observed six-line Mn (II) signal was monitored for 1 year. An inverse trend has been established between the photosynthetic efficiency of the plant and the measured content of Mn (II). The possibility of using EPR spectroscopy in studying ageing and in assessing stress situations in plants is considered.
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    URL: http://dx.doi.org/10.1007/s004680050223
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    Relation of water transport to leaf gas exchange properties in three mangrove species (2000)
    Springer
    Trees 14 (2000), S. 258-262 
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    ISSN: 0931-1890
    Keywords: Key words Hydraulic conductance ; Mangroves ; Photosynthesis ; Salinity ; Water use efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Mangrove species more tolerant to salinity may function with less efficient water transport, which may be related to more conservative water use. To test the hypothesis, we investigate the gas exchange and hydraulic properties of three mangrove species: Rhizophora mangle L., Laguncularia racemosa Gaert and Avicennia germinans (L.)L. Experiments were performed with adult plants growing naturally in the field under a salinity of 35‰. Gas exchange parameters showed that A. germinans had significantly higher photosynthetic rates, and lower stomatal conductance and transpiration rates, compared to the other two mangroves. In concert with this, instantaneous water use efficiency was significantly high in A. germinans, intermediate in L. racemosa and lowest in R. mangle. The hydraulic parameters of the three mangrove species were in the lowest end of the range reported for tropical trees. However, the three mangrove species exhibited measurable differences in hydraulic parameters related to the control of water requirements for maintenance of carbon gain. L. racemosa and A. germinans showed less efficient water transport at shoot level but were the more efficient species in water use at the leaf level in comparison to R. mangle.
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    Ontogenetic patterns of leaf CO2 exchange, morphology and chemistry in Betula pendula trees (2000)
    Springer
    Trees 14 (2000), S. 271-281 
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    ISSN: 0931-1890
    Keywords: Key words Betula pendula ; Photosynthesis ; Respiration ; Nutrients ; Leaf ontogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  In order to explore ontogenetic variation in leaf-level physiological traits of Betula pendula trees, we measured changes in mass- (A mass) and area-based (A area) net photosynthesis under light-saturated conditions, mass- (RSmass) and area-based (RSarea) leaf respiration, relative growth rate, leaf mass per area (LMA), total nonstructural carbohydrates (TNC), and macro- and micronutrient concentrations. Expanding leaves maintained high rates of A area, but due to high growth respiration rates, net CO2 fixation occurred only at irradiances 〉200 µmol photons m–2 s–1. We found that full structural leaf development is not a necessary prerequisite for maintaining positive CO2 balance in young birch leaves. Maximum rates of A area were realized in late June and early July, whereas the highest values of A mass occurred in May and steadily declined thereafter. The maintenance respiration rate averaged ≈8 nmol CO2 g–1 s–1, whereas growth respiration varied between 0 and 65 nmol CO2 g–1 s–1. After reaching its lowest point in mid-June, leaf respiration increased gradually until the end of the growing season. Mass and area-based dark respiration were significantly positively correlated with LMA at stages of leaf maturity, and senescence. Concentrations of P and K decreased during leaf development and stabilized or increased during maturity, and concentrations of immobile elements such as Ca, Mn and B increased throughout the growing season. Identification of interrelations between leaf development, CO2 exchange, TNC and leaf nutrients allowed us to define factors related to ontogenetic variation in leaf-level physiological traits and can be helpful in establishing periods appropriate for sampling birch leaves for diagnostic purposes such as assessment of plant and site productivity or effects of biotic or abiotic factors.
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    Changes in drought response strategies with ontogeny in Quercus rubra: implications for scaling from seedlings to mature trees (2000)
    Springer
    Oecologia 124 (2000), S. 8-18 
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    ISSN: 1432-1939
    Keywords: Key words Ontogeny ; Drought response ; Photosynthesis ; Water use efficiency ; Quercus rubra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We investigated scaling of physiological parameters between age classes of Quercus rubra by combining in situ field measurements with an experimental approach. In the in situ field study, we investigated changes in drought response with age in seedlings, juveniles, and mature trees of Q. rubra. Throughout the particularly dry summer of 1995 and the unusually wet summer of 1996 in New England, we measured water potential of leaves (ΨLeaf) and gas exchange of plants at three sites at the Harvard Forest in Petersham, Massachusetts. In order to determine what fraction of the measured differences in gas exchange between seedlings and mature trees was due to environment versus ontogeny, an experiment was conducted in which seedlings were grown under light and soil moisture regimes simulating the environment of mature trees. The photosynthetic capacity of mature trees was three-fold greater than that of seedlings during the wet year, and six-fold greater during the drought year. The seedling experiment demonstrated that the difference in photosynthetic capacity between seedlings and mature trees is comprised equally of an environmental component (50%) and an ontogenetic component (50%) in the absence of water limitation. Photosynthesis was depressed more severely in seedlings than in mature trees in the drought year relative to the wet year, while juveniles showed an intermediate response. Throughout the drought, the predawn leaf water potential (ΨPD) of seedlings became increasingly negative (–0.4 to –1.6 MPa), while that of mature trees became only slightly more negative (–0.2 to –0.5 MPa). Again, juveniles showed an intermediate response (–0.25 to –0.8 MPa). During the wet summer of 1996, however, there was no difference in ΨPD between seedlings, juveniles and mature trees. During the dry summer of 1995, seedlings were more responsive to a major rain event than mature trees in terms of ΨLeaf , suggesting that the two age classes depend on different water sources. In all age classes, instantaneous measurements of intrinsic water use efficiency (WUEi), defined as C assimilation rate divided by stomatal conductance, increased as the drought progressed, and all age classes had higher WUEi during the drought year than in the wet year. Mature trees, however, showed a greater ability to increase their WUEi in response to drought. Integrated measurements of WUE from C isotope discrimination (Δ) of leaves indicated higher WUE in mature trees than juveniles and seedlings. Differences between years, however, could not be distinguished, probably due to the strong bias in C isotope fractionation at the time of leaf production, which occurred prior to the onset of drought conditions in 1995. From this study, we arrive at two main conclusions:
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    Geographic pattern of genetic variation in photosynthetic capacity and growth in two hardwood species from British Columbia (2000)
    Springer
    Oecologia 123 (2000), S. 168-174 
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    ISSN: 1432-1939
    Keywords: Key words Intraspecific genetic variation ; Photosynthesis ; Frost hardiness ; Climate change ; Growing season
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Geographic patterns of intraspecific variations in traits related to photosynthesis and biomass were examined in two separate common garden experiments using seed collected from 26 Sitka alder (Alnus sinuata Rydb.) and 18 paper birch (Betula papyrifera Marsh.) populations from climatically diverse locations in British Columbia, Canada. Exchange rates of carbon dioxide and water vapour were measured on 2-year-old seedlings to determine the maximum net instantaneous photosynthetic rate, mesophyll conductance, stomatal conductance, and photosynthetic water use efficiency. Height, stem diameter, root and shoot dry mass and fall frost hardiness data were also obtained. Mean population maximum photosynthetic rate ranged from 10.35 to 14.57 µmol CO2 m–2 s–1 in Sitka alder and from 14.76 to 17.55 µmol CO2 m–2 s–1 in paper birch. Based on canonical correlation analyses, populations from locations with colder winters and shorter (but not necessarily cooler) summers had higher maximum photosynthetic rates implying the existence of an inverse relationship between leaf longevity and photosynthetic capacity. Significant canonical variates based on climatic variables derived for the seed collection sites explained 58% and 41% of variation in the rate of photosynthesis in Sitka alder and paper birch, respectively. Since growing season length is reflected in date of frost hardiness development, an intrinsic relationship was found between photosynthetic capacity and the level of fall frost hardiness. The correlation was particularly strong for paper birch (r=–0.77) and less strong for Sitka alder (r=–0.60). Mean population biomass accumulation decreased with increased climate coldness. These patterns may be consequential for evaluation of the impact of climate change and extension of the growing season on plant communities.
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    Photosynthetic responses to CO2 enrichment of four hardwood species in a forest understory (2000)
    Springer
    Oecologia 122 (2000), S. 11-19 
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    ISSN: 1432-1939
    Keywords: Key words Acclimation ; Atmospheric carbon dioxide ; Climate change ; Photosynthesis ; Shade tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We compared the CO2- and light-dependence of photosynthesis of four tree species (Acer rubrum, Carya glabra, Cercis canadensis, Liquidambar styraciflua) growing in the understory of a loblolly pine plantation under ambient or ambient plus 200 µl l–1 CO2. Naturally-established saplings were fumigated with a free-air CO2 enrichment system. Light-saturated photosynthetic rates were 159–190% greater for Ce. canadensis saplings grown and measured under elevated CO2. This species had the greatest CO2 stimulation of photosynthesis. Photosynthetic rates were only 59% greater for A. rubrum saplings under CO2 enrichment and Ca. glabra and L. styraciflua had intermediate responses. Elevated CO2 stimulated light-saturated photosynthesis more than the apparent quantum yield. The maximum rate of carboxylation of ribulose-1,5-bisphosphate carboxylase, estimated from gas-exchange measurements, was not consistently affected by growth in elevated CO2. However, the maximum electron transport rate estimated from gas- exchange measurements and from chlorophyll fluorescence, when averaged across species and dates, was approximately 10% higher for saplings in elevated CO2. The proportionately greater stimulation of light-saturated photosynthesis than the apparent quantum yield and elevated rates of maximum electron transport suggests that saplings growing under elevated CO2 make more efficient use of sunflecks. The stimulation of light-saturated photosynthesis by CO2 did not appear to correlate with shade-tolerance ranking of the individual species. However, the species with the greatest enhancement of photosynthesis, Ce. canadensis and L. styraciflua, also invested the greatest proportion of soluble protein in Rubisco. Environmental and endogenous factors affecting N partitioning may partially explain interspecific variation in the photosynthetic response to elevated CO2.
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    Testing the ecophysiological basis for the control of monoterpene concentrations along canopy profiles in thinned and unthinned balsam fir stands (2000)
    Springer
    Oecologia 124 (2000), S. 318-331 
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    ISSN: 1432-1939
    Keywords: Key words Balsam fir ; Carbon-nutrient balance ; Light ; Monoterpenes ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  To determine which ecophysiological factors appear to control monoterpene concentrations in balsam fir foliage [Abies balsamea (L.) P. Mill.], the percentage of photosynthetically active radiation (%PAR), specific leaf area (SLA), light-saturated photosynthesis (A max), and concentrations per unit leaf area of foliar nitrogen (N), total soluble sugars (TSS), starch and monoterpenes were measured on current-year needles from three canopy levels (upper, middle and lower) the year following a pre-commercial thinning. The thinning only modestly changed the light profile within the canopy. %PAR was negatively correlated with SLA (r 2=0.62 in June, r 2=0.53 in July and August) and positively correlated with foliar nitrogen concentrations (r 2=0.51) within the crown profile. The positive relationship between N and A max was quite weak (r 2=0.15), suggesting significant variations in non-photosynthetic N within the canopies. Total monoterpenes were positively correlated with both %PAR (r 2=0.29) and A max (r 2=0.27), and negatively correlated with SLA (r 2=0.30). Contrary to that predicted by the carbon-nutrient balance hypothesis, total monoterpenes were negatively and only very weakly correlated with the starch/N ratio (r 2=0.06) and were not significantly correlated with either the TSS/N or the [TSS+starch]/N ratios. Monoterpenes were positively correlated with both N and TSS, although the relationship varied with the phenological state of the foliage, i.e., monoterpenes were more highly correlated with TSS (r 2=0.67) (immature foliage) in June, and in July and August with N (r 2=0.63) (mature foliage). Thus, it appears that monoterpene concentrations may be controlled primarily by carbohydrate supply in the early growing season and later by enzymatic capacity. Data expressed on a dry weight basis showed a similar pattern.
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    Photosynthetic apparatus organization and function in the wild type and a chlorophyll b-less mutant of Chlamydomonas reinhardtii. Dependence on carbon source (2000)
    Springer
    Planta 211 (2000), S. 335-344 
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    ISSN: 1432-2048
    Keywords: Key words: Chlamydomonas (mutant) ; Chlorophyll b-less mutant ; Light-harvesting complex ; Photosynthesis ; Productivity (photosynthetic)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract.  The assembly, organization and function of the photosynthetic apparatus was investigated in the wild type and a chlorophyll (Chl) b-less mutant of the unicellular green alga Chlamydomonas reinhardtii, generated via DNA insertional mutagenesis. Comparative analyses were undertaken with cells grown photoheterotrophically (acetate), photomixotrophically (acetate and HCO− 3) or photoautotrophically (HCO− 3). It is shown that lack of Chl b diminished the photosystem-II (PSII) functional Chl antenna size from 320 Chl (a and b) to about 95 Chl a molecules. However, the functional Chl antenna size of PSI remained fairly constant at about 290 Chl molecules, independent of the presence of Chl b. Western blot and kinetic analyses suggested the presence of inner subunits of the Chl a-b light-harvesting complex of PSII (LHCII) and the entire complement of the Chl a-b light-harvesting complex of PSI (LHCI) in the mutant. It is concluded that Chl a can replace Chl b in the inner subunits of the LHCII and in the entire complement of the LHCI. Growth of cells on acetate as the sole carbon source imposes limitations in the photon-use efficiency and capacity of photosynthesis. These are manifested as a lower quantum yield and lower light-saturated rate of photosynthesis, and as lower variable to maximal (Fv/Fmax) chlorophyll fluorescence yield ratios. This adverse effect probably originates because acetate shifts the oxidation-reduction state of the plastoquinone pool, and also because it causes a decrease in the amount and/or activity of Rubisco in the chloroplast. Such limitations are fully alleviated upon inclusion of an inorganic carbon source (e.g. bicarbonate) in the cell growth medium. Further, the work provides evidence to show that transformation of green algae can be used as a tool by which to generate mutants exhibiting a permanently truncated Chl antenna size and a higher (per Chl) photosynthetic productivity of the cells.
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    Effect of heat stress on the inhibition and recovery of the ribulose-1,5-bisphosphate carboxylase/oxygenase activation state (2000)
    Springer
    Planta 212 (2000), S. 67-74 
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    ISSN: 1432-2048
    Keywords: Key words:Gossypium (heat stress ; Rubisco) ; Heat stress ; Photosynthesis ; Ribulose-1 ; 5-bisphosphate carboxylase/oxygenase ; Rubisco activase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Experiments were conducted to determine the relative contributions of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39) activation state vis-à-vis Rubisco activase and metabolite levels to the inhibition of cotton (Gossypium hirsutum L.) photosynthesis by heat stress. Exposure of leaf tissue in the light to temperatures of 40 or 45 °C decreased the activation state of Rubisco to levels that were 65 or 10%, respectively, of the 28 °C control. Ribulose-1,5-bisphosphate (RuBP) levels increased in heat-stressed leaves, whereas the 3-phosphoglyceric acid pool was depleted. Heat stress did not affect Rubisco per se, as full activity could be restored by incubation with CO2 and Mg2+. Inhibition and recovery of Rubisco activation state and carbon dioxide exchange rate (CER) were closely related under moderate heat stress (up to 42.5 °C). Moderate heat stress had negligible effect on Fv/Fm, the maximal quantum yield of photosystem II. In contrast, severe heat stress (45 °C) caused significant and irreversible damage to Rubisco activation, CER, and Fv/Fm. The rate of Rubisco activation after alleviating moderate heat stress was comparable to that of controls, indicating rapid reversibility of the process. However, moderate heat stress decreased both the rate and final extent of CER activation during dark-to-light transition. Treatment of cotton leaves with methyl viologen or an oxygen-enriched atmosphere reduced the effect of heat stress on Rubisco inactivation. Both treatments also reduced tissue RuBP levels, indicating that the amount of RuBP present during heat stress may influence the degree of Rubisco inactivation. Under both photorespiratory and non-photorespiratory conditions, the inhibition of the CER during heat stress could be completely reversed by increasing the internal partial pressure of CO2 (Ci). However, the inhibition of the CER by nigericin, a K+ ionophore, was not reversible when the Ci was increased at ambient or high temperature. Our results indicate that inhibition of photosynthesis by moderate heat stress is not caused by inhibition of the capacity for RuBP regeneration. We conclude that heat stress inhibits Rubisco activation via a rapid and direct effect on Rubisco activase, possibly by perturbing Rubisco activase subunit interactions with each other or with Rubisco.
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    Seasonal variation in primary production of microphytobenthos at the Isshiki intertidal flat in Mikawa Bay (2000)
    Springer
    Limnology 1 (2000), S. 133-138 
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    ISSN: 1439-863X
    Keywords: Key words Microphytobenthos ; Photosynthesis ; Seasonal and diurnal variation ; P-I curve
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seasonal variations in photosynthetic rates by microphytobenthos and phytoplankton at the Isshiki tidal flat in Mikawa Bay were measured with a 14C combustion method. In addition, diurnal variations in the photosynthetic rate and photosynthesis versus irradiance (P-I) curves were obtained through in situ incubation. The photosynthetic rate of microphytobenthos (annual average, 13.9 ± 6.4 mg C m−2 h−1) did not show a remarkable change, and they maintained a higher production rate than phytoplankton (annual average 9.0 ± 5.1 mg C m−2 h−1) throughout the year. The P-I curves from in situ experiments showed that the photosynthetic activity of microphytobenthos at the laboratory irradiance (250 μE m−2 s−1) was 56% of that at the maximum irradiance (1200 μE m−2 s−1) in situ. In the in situ experiments, the chlorophyll a concentration, photosynthetic rate, and activity of microphytobenthos varied greatly throughout the day, influenced by tidal submersion/emersion and daylight. From an analysis of these results, it is considered that microphytobenthos contributed greatly to primary production in this ecosystem throughout the year by adapting suitably to intertidal environments.
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    A polarographic, oxygen-selective, vibrating-microelectrode system for the spatial and temporal characterisation of transmembrane oxygen fluxes in plants (2000)
    Springer
    Planta 211 (2000), S. 384-389 
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    ISSN: 1432-2048
    Keywords: Key words: Olea europaea (O2 flux) ; Oscillation (O2 flux) ; Oxygen flux ; Oxygen-selective microelectrode ; Photosynthesis ; Root (O2 flux)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract.  A simple procedure is described for the fabrication of micrometer to nanometer-scale platinum electrodes to be used in a vibrating oxygen-selective system. The electrode was prepared by etching a fine platinum wire and insulating it with an electrophoretic paint. The dimensions allowed this electrode to be used with the “vibrating probe technique” in exploratory studies aimed at mapping and measuring the patterns of net influxes as well as effluxes of oxygen in Olea europaea L. leaves and roots with spatial and temporal resolutions of a few microns and a few seconds, respectively. The magnitude and spatial localisation of O2 influxes in roots was characterised by two distinct peaks. The first, in the division zone, averaged 38 ± 5 nmol m−2 s−1; the second, in the elongation region, averaged 68 ± 6 nmol m−2 s−1. Long-term records of oxygen influx in the elongation region of the root showed an oscillatory regime characterised by a fast oscillation with periods of about 8–9 min. In leaves, the system allowed the measurement of real-time changes in O2 evolution following changes in light. Furthermore, it was possible to obtain “topographical” images of the photosynthetically generated oxygen diffusing through different stomata from a region of the leaf of 120 μm × 120 μm. The combination of topographic and electrochemical information at the micrometer scale makes the system an efficient tool for studying biological phenomena involving oxygen diffusion.
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    Chlorophyll is not the primary photoreceptor for the stimulation of P-type H+ pump and growth in variegated leaves of Coleus×hybridus (2000)
    Springer
    Planta 212 (2000), S. 1-8 
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    ISSN: 1432-2048
    Keywords: Key words:Coleus×hybridus ; Electric photoresponse ; Leaf growth ; Photosynthesis ; Photomorphogenesis ; P-type H+-ATPase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. There has been persisting controversy over the role of photosynthesis in the stimulation of the plasma membrane H+-ATPase and growth of dicotyledonous leaves by light. To investigate this, we compared the effects of light on growth, H+ net efflux and membrane potential (Vm) of strips which contained either only chlorophyll-free (white) mesophyll cells or chlorophyll-containing (green) cells cut from variegated Coleus leaves. White mesophyll cells responded to white, blue and red light with a hyperpolarization of Vm, an acidification of the apoplast and a promotion of growth, all of which began after a lag of 2–7 min. In contrast, green mesophyll cells showed a biphasic light response in which the hyperpolarization and the acidification were preceded by a rapid depolarization of Vm and an alkalinization of the apoplast. Nevertheless, green and white tissues showed comparable growth promotions in response to light. The light response of the leaf mesophyll is a composite of two separate photosystems. The initial depolarization and alkalinization are mediated by photosynthesis and blocked by 3-(3,4-dichlorophenyl)-1,1-dimethylurea. The slower hyperpolarization, acidification and growth response, on the other hand, are clearly in response to light absorption by pigments other than chlorophyll.
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    URL: http://dx.doi.org/10.1007/s004250000365
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    Mycorrhizal fungi enhancement of growth and gas exchange of micropropagated guava plantlets (Psidium guajava L.) during ex vitro acclimatization and plant establishment (2000)
    Springer
    Mycorrhiza 10 (2000), S. 1-8 
    Details
    ISSN: 1432-1890
    Keywords: Arbuscular mycorrhiza ; Photosynthesis ; Stomatal conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Psidium guajava L.) plantlets was determined during acclimatization and plant establishment. Guava plantlets were asexually propagated through tissue culture and grown in a glasshouse for 18 weeks. Half of the plantlets were inoculated with a mixed endomycorrhiza isolate from Mexico, ZAC-19, containing Glomus diaphanum, G. albidum and G. claroides. Plantlets were fertilized with modified Long Ashton nutrient solution that supplied 11 μg P ml−1. Gas exchange measurements were taken at 2, 4, 8, and 18 weeks after inoculation using a portable photosynthesis system. All micropropagated guava plantlets survived transplant shock. After 6 weeks, mycorrhizal plantlets had greater shoot growth rates and leaf production than non-mycorrhizal plantlets. This also corresponded with increased photosynthetic rates and stomatal conductance of mycorrhizal plants. By 18 weeks, mycorrhizal plantlets had greater shoot length, leaf area, leaf, stem, and root dry mass. However, gas exchange was comparable among treatments, in part because the container size was restricting growth of the larger mycorrhizal plantlets. Non-mycorrhizal plantlets had greater leaf area ratios and specific leaf areas than mycorrhizal plantlets. Increased leaf tissue mineral levels of P, Mg, Cu, and Mo also occurred with mycorrhizal plantlets. Roots of inoculated guava plantlets were heavily colonized with arbuscules, vesicles and endospores. Guava plantlets were highly mycotrophic with a mycorrhizal dependency index of 103%.
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    URL: http://dx.doi.org/10.1007/s005720050280
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    Gas exchange and water relations of two Rocky Mountain shrub species exposed to a climate change manipulation (2000)
    Springer
    Plant ecology 146 (2000), S. 195-204 
    Details
    ISSN: 1573-5052
    Keywords: Artemisia ; Climate change ; Pentaphylloides ; Photosynthesis ; Rocky Mountains ; Subalpine ; Transpiration ; Water potential ; Water use efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gas exchange and water relations responses to warming were compared for two shrub species, Artemisia tridentata spp. vaseyana (Asteraceae), a widely distributed evergreen species of the Great Basin and the western slope of the Rocky Mountains, and Pentaphylloides floribunda (Rosaceae), a deciduous shrub limited in distribution to moist, high-elevation meadows. Plants were exposed to an in situ infrared (IR) climate change manipulation at the Rocky Mountain Biological Laboratory, near Crested Butte, CO. Measurements of gas exchange and water relations were made on the two species in July and August, 1993 from plants growing in situ in infrared-heated and control plots. Carbon dioxide uptake, water loss, leaf temperature, water use efficiency, and water potential were compared to test the hypothesis that leaf and soil responses to IR will cause leaf level changes in photosynthesis. Photosynthetic CO2 uptake and water use efficiency increased for A. tridentata (2.9 vs. 1.9 μmol m−2 s−1 and 1.2 vs. 0.7 mmol C/mol H2O) in the heated plots compared to the controls, while water potential was significantly lower in the heated plots (−1.1 vs. −0.5 MPa). The heating treatment decreased rates of photosynthesis for P. floribunda, but not significantly so. For A. tridentata, the results are consistent with the community-level changes observed with heating. Taken together, the evidence suggests that global warming is likely to result in increasing dominance of A. tridentata in subalpine meadow habitat now dominated by forbs.
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    URL: http://dx.doi.org/10.1023/A:1009863201751
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    The bryophyte paradox: tolerance of desiccation, evasion of drought (2000)
    Springer
    Plant ecology 151 (2000), S. 41-49 
    Details
    ISSN: 1573-5052
    Keywords: Ectohydry ; Photosynthesis ; Poikilohydry ; Protein synthesis ; Rehydration ; Water relations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Vascular plants represent one strategy of adaptation to the uneven and erratic supply of water on land. Desiccation-tolerant (DT) bryophytes represent an alternative, photosynthesising and growing when water is freely available, and suspending metabolism when it is not. By contrast with vascular plants, DT bryophytes are typically ectohydric, carrying external capillary water which can vary widely in quantity without affecting the water status of the cells. External water is important in water conduction, and results in bryophyte leaf cells functioning for most of the time at full turgor; water stress is a relatively brief transient phase before full desiccation. All bryophytes are C3 plants, and their cells are essentially mesophytic in important physiological respects. Their carbohydrate content shows parallels with that of maturing embryos of DT seeds. Initial recovery from moderate periods of desiccation is very rapid, and substantial elements of it appear to be independent of protein synthesis. Desiccation tolerance in effect acts as a device that evades the problems of drought, and in various adaptive features DT bryophytes are more comparable with (mesic) desert ephemerals or temperate winter annuals (but on a shorter time scale, with DT vegetative tissues substituting for DT seeds) than with drought-tolerant vascular plants.
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    Effects of extreme high temperature, drought and elevated CO2 on photosynthesis of the Mojave Desert evergreen shrub, Larrea tridentata (2000)
    Springer
    Plant ecology 148 (2000), S. 183-193 
    Details
    ISSN: 1573-5052
    Keywords: Chlorophyll fluorescence ; Drought ; Elevated CO2 ; High temperature ; Larrea tridenata ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The interaction of extreme temperature events with future atmospheric CO2 concentrations may have strong impacts on physiological performance of desert shrub seedlings, which during the critical establishment phase often endure temperature extremes in conjunction with pronounced drought. To evaluate the interaction of drought and CO2 on photosynthesis during heat stress, one-year-old Larrea tridentata[DC] Cov. seedlings were exposed to nine days of heat with midday air temperature maxima reaching 53 °C under three atmospheric CO2 concentrations (360, 550 and 700 μmol mol−1) and two water regimes (well-watered and droughted). Photosynthetic gas exchange, chlorophyll fluorescence and water potential responses were measured prior to, during and one week following the high temperature stress event. Heat stress markedly decreased net photosynthetic rate (A net), stomatal conductance (g s), and the photochemical efficiency of photosystem II (F v/F m) in all plants except for well-watered L. tridentata grown in 700 μmol mol−1 CO2. A net and g s remained similar to pre-stress levels in these plants. In droughted L. tridentata, A net was ca. 2× (in 550 μmol mol−1 CO2) to 3× (in 700 μmol mol−1 CO2) higher than in ambient-CO2-grown plants, while g s and F v/F m were similar and low in all CO2 treatments. Following heat stress, g s in all well-watered plants rose dramatically, exceeding pre-stress levels by up to 100%. In droughted plants, g s and A net rose only in plants grown at elevated CO2 following release from heat. This recovery response was strongest at 700 μmol mol−1 CO2, which returned to A net and g s values similar to pre-heat following several days of recovery. Extreme heat diminished the photosynthetic down-regulation response to growth at elevated CO2 under well-watered conditions, similar to the action of drought. Ambient-CO2-grown L. tridentata did not show significant recovery of photosynthetic capacity (A \max and CE) after alleviation of temperature stress, especially when exposed to drought, while plants exposed to elevated CO2 appeared to be unaffected. These findings suggest that elevated CO2 could promote photosynthetic activity during critical periods of seedling establishment, and enhance the potential for L. tridentata to survive extreme high temperature events.
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    A comparison of mechanisms of desiccation tolerance among three angiosperm resurrection plant species (2000)
    Springer
    Plant ecology 151 (2000), S. 29-39 
    Details
    ISSN: 1573-5052
    Keywords: Antioxidants ; Mechanical stress ; Oxidative stress ; Photosynthesis ; Vacuolation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mechanisms of protection against mechanical and oxidative stress were identified and compared in the angiosperm resurrection plants Craterostigma wilmsii, Myrothamnus flabellifolius and Xerophyta humilis. Drying-induced ultrastructural changes within mesophyll cells were followed to gain an understanding of the mechanisms of mechanical stabilisation. In all three species, water filled vacuoles present in hydrated cells were replaced by several smaller vacuoles filled with non-aqueous substances. In X. humilis, these occupied a large proportion of the cytoplasm, preventing plasmalemma withdrawal and cell wall collapse. In C. wilmsii, vacuoles were small but extensive cell wall folding occurred to prevent plasmalemma withdrawal. In M. flabellifolius, some degree of vacuolation and wall folding occurred, but neither were sufficient to prevent plasmalemma withdrawal. This membrane was not ruptured, possibly due to membrane repair at plasmodesmata junctions where tearing might have occurred. In addition, the extra-cytoplasmic compartment appeared to contain material (possibly similar to that in vacuoles) which could facilitate stabilisation of dry cells. Photosynthesis and respiration are particularly susceptible to oxidative stress during drying. Photosynthesis ceased at high water contents and it is proposed that a controlled shut down of this metabolism occurred in order to minimise the potential for photo-oxidation. The mechanisms whereby this was achieved varied among the species. In X. humilis, chlorophyll was degraded and thylakoid membranes dismantled during drying. In both C. wilmsii and M. flabellifolius, chlorophyll was retained, but photosynthesis was stopped due to chlorophyll shading from leaf folding and anthocyanin accumulation. Furthermore, in M. flabellifolius thylakoid membranes became unstacked during drying. All species continued respiration during drying to 10% relative water content, which is proposed to be necessary for energy to establish protection mechanisms. Activity of antioxidant enzymes increased during drying and remained high at low water contents in all species, ameliorating free radical damage from both photosynthesis and respiration. The nature and extent of antioxidant upregulation varied among the species. In C. wilmsii, only ascorbate peroxidise activity increased, but in M. flabellifolius and X. humilis ascorbate peroxidise, glutathione reductase and superoxide dismutase activity increased, to various extents, during drying. Anthocyanins accumulated in all species but this was more extensive in the homoiochlorophyllous types, possibly for protection against photo-oxidation.
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    Single-cell, real-time measurements of extracellular oxygen and proton fluxes fromSpirogyra grevilleana (2000)
    Springer
    Protoplasma 212 (2000), S. 80-88 
    Details
    ISSN: 1615-6102
    Keywords: Alternative oxidase ; Photosynthesis ; Respiration ; Self-referencing microelectrode ; Spirogyra gre illeana ; Vibrating probe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have adapted the self-referencing microelectrode technique to allow sensitive and noninvasive measurement of oxygen fluxes around single cells. The self-referencing technique is based on the translational movement of a selective microelectrode through the gradient next to the cell wall or membrane. The electrode is moved at a known frequency and between known points. The differential electrode output values are converted into a directional measurement of flux by the Fick equation. By coupling the newly developed oxygen-selective self-referencing electrochemical microelectrode (SREM-O2) system with self-referencing ionselective proton measurements (SRIS-H+) we have characterized oxygen and proton fluxes from a single cell of the filamentous green algaSpirogyra gre illeana (Hass.). Oxygen showed a net efflux and protons showed a net influx when the cell was illuminated. These photosynthesis-dependent fluxes were found to be spatially associated with the chloroplasts and were sensitive to treatment with dichlorophenyldimethylurea. In the dark the directions of oxygen and proton fluxes were reversed. This oxygen influx was associated with mitochondrial respiration and was reduced by 78% when the cells was treated with 0.5 mM KCN. The residual cyanide-resistant respiration was inhibited by the application of 5 mM salicylhydroxamic acid, an inhibitor of the alternative oxidase. Similarly the cytochrome pathway was also inhibited by the presence of 20 μM NO, while the cyanide-resistant alternative oxidase was not. These results demonstrate the use of the newly developed SREM-O2 system to measure and characterize metabolic fluxes at a level of sensitivity that allows for subcellular resolution. These measurements, in conjunction with SERIS-H+ measurements, have led to new insights in our understanding of basic cellular physiology in plant cells.
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    Protein domains required for formation of stable monomeric Lhca1- and Lhca4-complexes (2000)
    Springer
    Photosynthesis research 63 (2000), S. 217-224 
    Details
    ISSN: 1573-5079
    Keywords: antenna ; Lhca1 ; Lhca4 ; LHC I-730 ; light-harvesting complexes ; pigment–protein complex ; Photosystem I ; Photosynthesis ; protein structure ; reconstitution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The peripheral light-harvesting complex of Photosystem I consists of two subpopulations, LHC I-680 and LHC I-730. The latter is composed of the two apoproteins Lhca1 and Lhca4. Recently, reconstitution of monomeric LHC I using bacterially overexpressed Lhca1 or Lhca4 was achieved. In order to obtain insight into the structure requirements for formation of monomeric light-harvesting complexes, we produced a series of N- and C-terminal deletion mutants and used the overexpressed proteins for reconstitution experiments. We found the entire extrinsic N-terminal region dispensable for monomer formation in Lhca1 and Lhca4. Also at the C-terminus, both subunits revealed similarity since all amino acids up to the end of the fourth helix could be removed without abolishing monomer formation. In connection with former corresponding results for Lhcb1, the dispensability of these regions appears to be a general feature in LHC-formation. In LHC I, however, a stabilising effect can be ascribed to these regions since the yield of complexes was decreased. In the majority of the mutant LHC I versions no effect on pigment binding was detected. However, in the LHC with the most extensively N-terminally truncated mutant of Lhca4 a dramatic shift in the 77 K fluorescence emission to shorter wavelengths was observed. This suggests that chlorophylls involved in long wavelength fluorescence emission are located in the chlorophyll array located towards the stromal face of the thylakoid membrane assuming a pigment arrangement corresponding to that in LHC II and CP29.
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    URL: http://dx.doi.org/10.1023/A:1006499517613
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    Effects of long-term CO2 enrichment and nutrient availability in Norway spruce. I. Phenology and morphology of branches (1999)
    Springer
    Trees 13 (1999), S. 188-198 
    Details
    ISSN: 0931-1890
    Keywords: Key words Picea abies ; Photosynthesis ; Nitrogen ; Temperature ; Shoot growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Branches of 30-year-old Norway spruce [Picea abies (L.) Karst.] trees were enclosed in ventilated, transparent plastic bags and flushed with air containing ambient (A≈370 μmol CO2 mol–1) or ambient plus 340 μmol CO2 mol–1 (EL). Light-saturated photosynthesis was on average 56% higher in EL compared to A. Branch phenology and morphology were strongly related to nitrogen concentration (mg g–1 dry mass) in the foliage and to elevated temperatures in the bags, but no direct effect of EL was found. In 1995, budbreak occurred on average 4 days earlier in the bags compared to the control branches, which was partly explained by the temperature elevation in the bags. No nutrient or EL effect on budbreak was found. Increases in temperature and nitrogen supply increased shoot growth: together they explained 76% of the variation in the extension rate, 63% of the variation in extension duration and 65% of the variation in final length of leading shoots. Shoot morphology was altered both by increased nitrogen availability and by the enclosure induced environmental changes inside the bags, leading to reduced mutual shading between needles. Specific needle area (SNA) was lower in EL, but this was related to lower nitrogen concentrations. Total dry mass of the branches was unaffected by EL. It is concluded that treating individual branches of Norway spruce with elevated CO2 does not increase branch growth. The nutrient status of the branch and climate determine its growth, i.e. its sink strength for carbon. Increased export of carbohydrates to the rest of the tree is probable in EL treated branches.
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    Photosynthetic acclimation in eastern hemlock [Tsuga canadensis (L.) Carr.] seedlings following transfer of shade-grown seedlings to high light (1999)
    Springer
    Trees 13 (1999), S. 117-124 
    Details
    ISSN: 0931-1890
    Keywords: Key words Eastern hemlock ; Photosynthesis ; Chlorophyll fluorescence ; Light acclimation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  We studied photosynthetic acclimation of eastern hemlock [Tsuga canadensis (L.) Carr.] seedlings in the first month after sudden exposure of shade-grown seedlings to full sunlight. In a greenhouse experiment, seedlings were grown under full sun or 80% shade, and after 7 months, a sample of the shaded trees was transferred to full sun in the greenhouse. Photosynthetic responses of shaded, transferred, and sun trees were followed over the course of 26 days to track short to medium-term acclimation responses. A partial acclimation of photosynthesis at high light occurred in pre-existing (formed in the previous environment) and new foliage of transferred seedlings. This was associated with non-stomatal limitations to photosynthesis. Pre-existing foliage of transferred plants had a prolonged reduction in the ratio of variable to maximal fluorescence, and a limited capacity to adjust photochemical quenching or photosystem II quantum yield in the light to increasing light intensity compared to sun foliage, and apparently had some difficulty sustaining non-photochemical quenching. Seedling survival was only 58% among transferred seedlings, compared to 80% and 100% in the shade or sun groups, respectively. Photosystem II quantum yield in the light, and photochemical and non-photochemical quenching were similar between newly formed foliage of transferred and sun plants. These findings indicate that eastern hemlock depends strongly on the production of new foliage for photosynthetic adjustments to high light, and that development of photosynthetic competence may be a gradual process that occurs over successive foliar production cycles.
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    Drought effects on photosynthesis of the mangrove, Avicennia germinans, under contrasting salinities (1999)
    Springer
    Trees 13 (1999), S. 125-130 
    Details
    ISSN: 0931-1890
    Keywords: Key words A. germinans ; Fluorescence ; Photosynthesis ; Salinity ; Water use efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Drought effects on leaf photosynthesis of A. germinans growing under two contrasting salinities were studied in a Venezuelan fringe mangrove. During both wet and dry seasons, severe chronic-photoinhibition at predawn was not observed but strong down regulation occurred at midday during both seasons. Carbon assimilation rates (A, μmol CO2 m−2 s−1) declined during the dry season from 11.9±1.8 to 7.0±1.5 and from 9.6±2.0 to 4.7±2.5 in plants from low and high salinity sites, respectively. Changes in carbon assimilation per unit of chlorophyll (A/Chl, mmol CO2 mol−1 Chl) were from 31.6±4.7 to 20.5±4.3 and from 21.9±4.7 to 15.2±8.2 in the low and high salinity plants, respectively. Therefore, neither changes in Chl nor seasonal differences in photoprotective down regulation could account fully for the decrease in leaf photosynthesis during drought. A reduction in CO2 diffusion due to lowered stomatal conductance was not large enough to explain such a dramatic effect of drought on leaf photosynthesis. Stomatal response could be mitigated by the capability of A. germinans for osmotic adjustment under high salinity and/or drought. However, this intracellular salt accumulation may reduce carbon assimilation capacity further by decreasing the metabolism of leaf cells, increasing dark respiration and/or photorespiration.
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    Photosynthesis and water relations of four oak species: impact of flooding and salinity (1999)
    Springer
    Trees 13 (1999), S. 178-187 
    Details
    ISSN: 0931-1890
    Keywords: Key words Inundation ; Salt tolerance ; Photosynthesis ; Conductance ; Water relations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  As global climate changes, sea level rise and increased frequency of hurricanes will expose coastal forests to increased flooding and salinity. Quercus species are frequently dominant in these forest, yet little is known about their salinity tolerance, especially in combination with flooding. In this study, 1-year-old seedlings of Quercus lyrata Walt. (overcup oak), Q. michauxii Nutt. (swamp chestnut oak), Q. nigra L. (water oak), and Q. nuttallii Palmer (Nuttall oak) were chronically (simulating sea level rise) and acutely (simulating hurricane storm surge) exposed to increased flooding and salinity, individually and in combination. The four species demonstrated two response patterns of photosynthesis (A), conductance, and leaf water potential, apparently related to their relative flood tolerance. In Q. lyrata, Q. nuttallii, and Q. nigra (moderately flood-tolerant), A was not immediately reduced after the initiation of the freshwater flooding, but was reduced as the duration of flooding increased. In the second pattern, demonstrated by the weakly flood-tolerant Q. michauxii, A was immediately reduced by freshwater flooding with an increasing impact over time. Watering with 2 parts per thousand (ppt) saline water did not consistently reduce A, but flooding with 2 ppt reduced A of all species, similar to the response with freshwater flooding. Photosynthesis of all species was reduced by 6 ppt watering or flooding, with the latter treatment killing all species within 8 weeks. When acutely exposed to 30 ppt salinity, A was quickly and severely reduced regardless of whether the seedlings were watered or flooded. Acutely flooded seedlings exposed to high salinity died within 2 weeks, but seedlings watered with 30 ppt saline water recovered and A was not reduced the following spring. As saline flooding of coastal areas increases due to sea level rise, photosynthesis of these species will be differentially affected based primarily on their flood tolerance. This suggests that increased flooding associated with sea level rise will impact these tree species to a greater extent than small increases in soil salinity. High salinity accompanying storm surges will be very harmful to all of these species.
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    Temperature and humidity effects on branchlet gas-exchange in white spruce: an explanation for the increase in transpiration with branchlet temperature (1999)
    Springer
    Trees 14 (1999), S. 161-168 
    Details
    ISSN: 0931-1890
    Keywords: Key words Picea glauca ; Transpiration ; Stomatal conductance ; Photosynthesis ; Water viscosity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  In situ gas-exchange data, for branchlets of white spruce [Picea glauca (Moench) Voss.] in a mature mixed-wood boreal forest in central Canada (53°44´N 105°14´W), were subjected to a multiple regression analysis. Vapor pressure deficit (VPD) and branchlet temperature (tleaf) were both significant predictors (P〈0.0001) of stomatal conductance to water vapor (gsw) and net photosynthesis (An), together explaining 67 and 64% of the variation in gsw and An, respectively. Since VPD and tleaf were autocorrelated in these field data, but also to further explore the nature of independent effects of temperature and humidity on water and CO2 exchange in white spruce, steady-state gas-exchange was performed on well-watered greenhouse-grown seedlings of white spruce. Results from laboratory experiments supported the following conclusions: (1) Transpiration (E) increases with VPD to an inflection point that increases linearly with tleaf. This tleaf effect on E could not be explained by trends in VPD, RH, An or PFD. Rather, our data support a model in which E and gsw are influenced by the balance between ’supply’ and ’loss’ of water to and from leaf tissue, respectively. The supply of water appears to be in accordance with Darcy’s law, where supply of water is proportional to the driving gradient in pressure/ tension, specific permeability (k), and inverse of water viscosity (n –1). Approximately half of the increase in E could be explained by the linear increase in n –1 with increasing tleaf. We propose that increases in k explain the remainder of the increase in E with tleaf. (2) VPD and tleaf appear to have independent effects on gsw. In contrast, RH effects on gsw or E were subtle and could be explained by a combination of effects of tleaf and VPD. (3) An was affected primarily by tleaf, being reduced at low (10°C) and high (40°C) temperatures, and only indirectly by humidity parameters via stomatal conductance, viz. intercellular CO2 concentrations. Our results have implications for the prediction of water fluxes from plants and canopies in areas where plant temperatures vary diurnally or seasonally.
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    Protection against photoinhibition in the alpine plant Geum montanum (1999)
    Springer
    Oecologia 119 (1999), S. 149-158 
    Details
    ISSN: 1432-1939
    Keywords: Key words Electron transport ; Low temperature ; Photosynthesis ; Photosystems I and II ; Water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Geum montanum L. is an alpine plant usually found at altitudes between 1700 and 2600 m. Its wintergreen leaves can be subjected to very low temperatures and at the same time receive high photon flux densities at the beginning of the growth season when the snow melts. We report results of a study, performed with classical methods of biophysics, showing that leaves of G. montanum were remarkably tolerant to sunlight even at low temperatures. This tolerance results from the interplay of photorespiration and CO2 photosassimilation. When temperatures approach 0°C, responses include stomatal opening and CO2 uptake even under desiccation stress. This permits linear electron transport that is sufficient to avoid the excessive reduction of the electron transport chain which is known to lead to photodamage. In addition, excitation energy was shifted from photosystem (PS)II to PSI which is a very efficient energy quencher. Sensitivity of P700 in PSI to oxidation by far-red light was decreased and rates of dark reduction of photooxidized P700 were increased by actinic illumination, suggesting activation of cyclic electron transport. Consistent with this, far-red light was able to decrease the quantum yield of PSII (measured by the F v/F m ratio of chlorophyll fluorescence). We suggest that cyclic electron transport decreases the lumenal pH under strong light. In the presence of zeaxanthin, this increases energy dissipation at the PSII level. At low temperatures, P700 remained strongly oxidized under high irradiation while the primary electron acceptor of PSII, QA, was largely reduced. This shows efficient control of electron transport presumably at the level of the cytochrome b/f complex and suggests formation of a protective transthylakoid proton gradient even when linear electron transport is much reduced in the cold. Thus, several mechanisms cooperate to effectively protect the photosynthetic apparatus of G. montanum from photodamage. We see no indication of destructive “photostress” in this species during the growth season under alpine low-temperature and drought conditions.
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    Leaf construction cost, nutrient concentration, and net CO2 assimilation of native and invasive species in Hawaii (1999)
    Springer
    Oecologia 121 (1999), S. 183-192 
    Details
    ISSN: 1432-1939
    Keywords: Key words Cost of construction ; Life forms ; Nitrogen use efficiency ; Photosynthesis ; Specific leaf area
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of biological invasions are most evident in isolated oceanic islands such as the Hawaiian Archipelago, where invasive plant species are rapidly changing the composition and function of plant communities. In this study, we compared the specific leaf area (SLA), leaf tissue construction cost (CC), leaf nutrient concentration, and net CO2 assimilation (A) of 83 populations of 34 native and 30 invasive species spanning elevation and substrate age gradients on Mauna Loa volcano in the island of Hawaii. In this complex environmental matrix, where annual precipitation is higher than 1500 mm, we predicted that invasive species, as a group, will have leaf traits, such as higher SLA and A and lower leaf CC, which may result in more efficient capture of limiting resources (use more resources at a lower carbon cost) than native species. Overall, invasive species had higher SLA and A, and lower CC than native species, consistent with our prediction. SLA and foliar N and P were 22.5%, 30.5%, and 37.5% higher, respectively, in invasive species compared to native ones. Light-saturated photosynthesis was higher for invasive species (9.59 μmol m−2 s−1) than for native species (7.31 μmol m−2 s−1), and the difference was larger when A was expressed on a mass basis. Leaf construction costs, on the other hand, were lower for the invasive species (1.33 equivalents of glucose g−1) than for native species (1.37). This difference was larger when CC was expressed on an area basis. The trends in the above traits were maintained when groups of ecologically equivalent native and invasive species (i.e., sharing similar life history traits and growing in the same habitat) were compared. Foliar N and P were significantly higher in invasive species across all growth forms. Higher N may partially explain the higher A of invasive species. Despite relatively high N, the photosynthetic nitrogen use efficiency of invasive species was 15% higher than that of native species. These results suggest that invasive species may not only use resources more efficiently than native species, but may potentially demonstrate higher growth rates, consistent with their rapid spread in isolated oceanic islands.
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    URL: http://dx.doi.org/10.1007/s004420050920
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    Survival tactics of Ranunculus species in river floodplains (1999)
    Springer
    Oecologia 118 (1999), S. 1-8 
    Details
    ISSN: 1432-1939
    Keywords: Key words Aerenchyma ; Ranunculus ; Shoot elongation ; Photosynthesis ; Survival of flooding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The flooding resistance of four Ranunculus species was studied under controlled conditions and related to the tactics used by these species to survive in their natural habitat in river floodplains. R. bulbosus, a species from seldom-flooded river levées, was relatively intolerant of both waterlogging and complete submergence, due to a constitutively low level of aerenchyma in the root system. This lack of gas spaces resulted in high mortality rates during flooding treatments and an inability to use photosynthetically derived oxygen for root respiration during complete submergence. The pioneer R. sceleratus, predominantly abundant in low lying mudflats, was very resistant to waterlogging and shallow floods. Due to its constitutively high root porosity and its ability to greatly increase the elongation rate of petioles under water this species can ameliorate flooding stress. However, when leaf blades of R. sceleratus were unable to reach the water surface, this species died as quickly as the flooding-intolerant R. bulbosus. This indicates that fast elongation of petioles under water competes for energy and respirable reserves with maintenance processes. R. repens, a species from lower, frequently inundated floodplains, was very tolerant of prolonged waterlogging and submergence. Its high resistance to complete submergence under continuous darkness indicates that this species tolerates hypoxic and/or anoxic tissue conditions via metabolic adjustments. Lysigenous aerenchyma was also induced in the primary root system and in newly developed laterals, and it was able to use oxygen generated by underwater photosynthesis, for root respiration. R. acris, a species from less frequently flooded areas, was as resistant to waterlogging and submergence in the light as R. repens. However, it has a lower resistance than R. repens to complete submergence in the dark. A submergence pre-treatment increased the maximum net underwater photosynthetic rate in R. bulbosus, whereas a significant decrease of light compensation points was observed in R. repens when it had previously been submerged. This study shows that Ranunculus species exhibit various strategies to cope with different flooding conditions. R. repens responds to flooding by its tolerance mechanism and R. sceleratus by avoidance. R. acris ameliorates submergence and R. bulbosus was not able to adapt high water tables.
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    URL: http://dx.doi.org/10.1007/s004420050696
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    Analysis of differences in photosynthetic nitrogen use efficiency of alpine and lowland Poa species (1999)
    Springer
    Oecologia 120 (1999), S. 19-26 
    Details
    ISSN: 1432-1939
    Keywords: Key words Alpine ; Nitrogen ; Lowland ; Photosynthesis ; Photosynthetic nitrogen use efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study investigates factors determining variation in photosynthetic nitrogen use efficiency (φN) in seven slow- and fast-growing Poa species from altitudinally contrasting sites. The species and their environmental origin were (in order of increasing relative growth rate): two alpine (Poa fawcettiae and P. costiniana), one sub-alpine (P. alpina) and three temperate lowland perennials (P. pratensis, P. compressa and P. trivialis), as well as one temperate lowland annual (P. annua). Plants were grown hydroponically under identical conditions with free access to nutrients in a growth room. Photosynthesis per unit leaf area measured at growth irradiance (500 μmol m−2 s−1) was slightly higher in the slow-growing alpine species. At saturating light intensities, photosynthesis was considerably higher in the alpine species than in the lowland species. Carboxylation capacity and Rubisco content per unit leaf area were also greater in the alpine species. Despite variation between the species, the in vivo specific activity of Rubisco showed little relationship to relative growth rate or photosynthetic rate. Both at light saturation and at the growth irradiance, φN was lowest in the slow-growing alpine species P. fawcettiae, P. costiniana and P. alpina, and highest in the fast-growing P. compressa and P. annua. The proportion of leaf nitrogen that was allocated to photosynthetic capacity and the in vivo catalytic constant of Rubisco accounted for most of the variation in φN at light saturation. Minor variations in intercellular CO2 partial pressure also contributed to some extent to the variations in φN at light saturation. The low φN values at growth irradiance exhibited by the alpine species were additionally due to a lower percentage utilisation of their high photosynthetic capacity compared to the lowland species.
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    URL: http://dx.doi.org/10.1007/s004420050828
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    Foliage physiology and biochemistry in response to light gradients in conifers with varying shade tolerance (1999)
    Springer
    Oecologia 120 (1999), S. 183-192 
    Details
    ISSN: 1432-1939
    Keywords: Key words Radiation gradients ; Photosynthesis ; Confiers Shade tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To examine the predictability of leaf physiology and biochemistry from light gradients within canopies, we measured photosynthetic light-response curves, leaf mass per area (LMA) and concentrations of nitrogen, phosphorus and chlorophyll at 15–20 positions within canopies of three conifer species with increasing shade tolerance, ponderosa pine [Pinus ponderosa (Laws.)], Douglas fir [Pseudotsuga menziesii (Mirb.) Franco], and western hemlock [Tsuga heterophylla (Raf.) Sarg.]. Adjacent to each sampling position, we continuously monitored photosynthetically active photon flux density (PPFD) over a 5-week period using quantum sensors. From these measurements we calculated FPAR: integrated PPFD at each sampling point as a fraction of full sun. From the shadiest to the brightest canopy positions, LMA increased by about 50% in ponderosa pine and 100% in western hemlock; Douglas fir was intermediate. Canopy-average LMA increased with decreasing shade tolerance. Most foliage properties showed more variability within and between canopies when expressed on a leaf area basis than on a leaf mass basis, although the reverse was true for chlorophyll. Where foliage biochemistry or physiology was correlated with FPAR, the relationships were non-linear, tending to reach a plateau at about 50% of full sunlight. Slopes of response functions relating physiology and biochemistry to ln(FPAR) were not significantly different among species except for the light compensation point, which did not vary in response to light in ponderosa pine, but did in the other two species. We used the physiological measurements for Douglas fir in a model to simulate canopy photosynthetic potential (daily net carbon gain limited only by PPFD) and tested the hypothesis that allocation of carbon and nitrogen is optimized relative to PPFD gradients. Simulated photosynthetic potential for the whole canopy was slightly higher (〈10%) using the measured allocation of C and N within the canopy compared with no stratification (i.e., all foliage identical). However, there was no evidence that the actual allocation pattern was optimized on the basis of PPFD gradients alone; simulated net carbon assimilation increased still further when even more N and C were allocated to high-light environments at the canopy top.
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    URL: http://dx.doi.org/10.1007/s004420050847
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    Regulation of the photosynthetic electron transport chain (1999)
    Springer
    Planta 209 (1999), S. 250-258 
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    ISSN: 1432-2048
    Keywords: Keywords:ΔpH ; Electron transport ; Photosynthesis ; Photosynthetic control ; Redox regulation ; Silene (photosynthesis)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The regulation of electron transport between photosystems II and I was investigated in the plant Silene dioica L. by means of measurement of the kinetics of reduction of P700 following a light-to-dark transition. It was found that, in this species, the rate constant for P700 reduction is sensitive to light intensity and to the availability of CO2. The results indicated that at 25 °C the rate of electron transport is down-regulated by approximately 40–50% relative to the maximum rate achievable in saturating CO2 and that this down-regulation can be explained by regulation of the electron transport chain itself. Measurements of the temperature sensitivity of this rate constant indicated that there is a switch in the rate-limiting step that controls electron transport at around 20 °C: at higher temperatures, CO2 availability is limiting; at lower temperatures some other process regulates electron transport, possibly a diffusion step within the electron transport chain itself. Regulation of electron transport also occurred in response to drought stress and sucrose feeding. Measurements of non-photochemical quenching of chlorophyll fluorescence did not support the idea that electron transport is regulated by the pH gradient across the thylakoid membrane, and the possibility is discussed that the redox potential of a stromal component may regulate electron transport.
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    URL: http://dx.doi.org/10.1007/s004250050629
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    Hydroponic treatment with salicylic acid decreases the effects of chilling injury in maize (Zea mays L.) plants (1999)
    Springer
    Planta 208 (1999), S. 175-180 
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    ISSN: 1432-2048
    Keywords: Key words: Antioxidant enzyme ; Cold stress ; Photosynthesis ; Salicylic acid ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The addition of 0.5 mM salicylic acid (SA) to the hydroponic growth solution of young maize (Zea mays L.) plants under normal growth conditions provided protection against subsequent low-temperature stress. This observation was confirmed by chlorophyll fluorescence parameters and electrolyte leakage measurements. In addition, 1 d of 0.5 mM SA pre-treatment decreased net photosynthesis, stomatal conductivity and transpiration at the growth temperature (22/20 °C). Since there was only a slight decrease in the ratio of variable to maximal fluorescence (Fv/Fm) the decrease in photosynthetic activity is not due to a depression in photosystem II. The analysis of antioxidant enzymes showed that whereas SA treatment did not cause any change in ascorbate peroxidase (EC 1.11.1.11) and superoxide dismutase (EC 1.15.1.1) activities, there was a decrease in catalase (EC 1.11.1.6) activity, and an increase in guaiacol peroxidase (EC 1.11.1.7) and glutathione reductase (EC 1.6.4.2) activities after the 1-d SA treatment at 22/20 °C. In native polyacrylamide gels there was, among the peroxidase isoenzymes, a band which could be seen only in SA-treated plants. It is suggested that the pre-treatment of maize plants with SA at normal growth temperature may induce antioxidant enzymes which lead to increased chilling tolerance.
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    URL: http://dx.doi.org/10.1007/s004250050547
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    The effect of light on membrane potential, apoplastic pH and cell expansion in leaves of Pisum sativum L. var. Argenteum. (1999)
    Springer
    Planta 208 (1999), S. 188-195 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Cell expansion ; Electric photoresponse ; Mesophyll ; Photosynthesis ; Pisum (Argenteum mutant) ; Plasma-membrane H+-ATPase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The connection between three light responses of green leaf cells-membrane potential (Vm), H+ net efflux and growth, was analyzed. Illumination of mesophyll cells in leaves from Argenteum peas caused two rapid responses: (i) a de- and repolarization of Vm and (ii) an alkalinization of the apoplast. The rapid responses were completely eliminated by the photosynthetic inhibitor 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU) but not affected by ortho-vanadate, an inhibitor of the plasma membrane (PM) H+-ATPase. The rapid changes were followed by a set of delayed responses: (i) a slow, gradual hyperpolarization of Vm, (ii) a gradual acidification of the mesophyll apoplast and (iii) an increased rate of elongation. These three light responses persisted under DCMU but were completely eliminated by vanadate. The data show that the delayed (in contrast to the rapid) responses were due to a stimulation of PM H+ pumps which occurred independently of non-cyclic photosynthetic electron transport and the “dark” processes depending on it. When the rapid responses were blocked by DCMU, light-induced acidification, hyperpolarization of the membrane potential and growth proceeded simultaneously. A shared (4-min) lag phase indicated slower signal processing in mesophyll than in epidermal cells where light stimulation of PM H+ pumps was rapid.
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    Photoadaptation of two members of the Chlorophyta (Scenedesmus and Chlorella) in laboratory and outdoor cultures: changes in chlorophyll fluorescence quenching and the xanthophyll cycle (1999)
    Springer
    Planta 209 (1999), S. 126-135 
    Details
    ISSN: 1432-2048
    Keywords: Key words:Chlorella ; Electron transport rate ; Non-photochemical quenching ; Photosynthesis ; Scenedesmus ; Xanthophyll cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The role of the xanthophyll cycle in the adaptation of two chlorococcal algae Scenedesmus quadricauda and Chlorella sorokiniana to high irradiance was studied under laboratory and outdoor conditions. We wished to elucidate whether the xanthophyll cycle plays a key role in dissipating the excesses of absorbed light, as in higher plants, and to characterise the relationship between chlorophyll fluorescence parameters and the content of xanthophyll-cycle pigments. The xanthophyll cycle was found to be operative in both species; however, its contribution to overall non-photochemical quenching (NPQ) could only be distinguished in Scenedesmus (15–20% of total NPQ). The Scenedesmus cultures showed a larger pool of xanthophyll-cycle pigments than Chlorella, and lower sensitivity to photoinhibition as judged from the reduction of maximum quantum yield of photosystem II. In general, both algae had a larger xanthophyll-cycle pool when grown outdoors than in laboratory cultures. Comparing the two species, Scenedesmus exhibited a higher capacity to adapt to high irradiance, due to an effective quenching mechanism and high photosynthetic capacity; in contrast, Chlorella represents a species with a larger antennae system, less-efficient quenching and lower photosynthetic performance. Non-photochemical quenching (NPQ) induced through the xanthophyll cycle can, to a limited extent, represent a regulatory factor in diluted algal cultures grown in outdoor solar photobioreactors, as well as in natural algal phytoplankton populations exposed transiently to high irradiance. However, it does not play an appreciable role in dense, well-mixed microalgal suspensions.
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    URL: http://dx.doi.org/10.1007/s004250050614
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    Acclimation of the summer annual species, Lolium temulentum, to CO2 enrichment (1999)
    Springer
    Planta 210 (1999), S. 104-114 
    Details
    ISSN: 1432-2048
    Keywords: Keywords: Carbohydrate ; CO2 enrichment ; Lolium (CO2 enrichment) ; Photosynthesis ; Respiration ; Ribulose-1 ; 5-bisphosphate carboxylase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Lolium temulentum L. Ba 3081 was grown hydroponically in air (350 μmol mol−1 CO2) and elevated CO2 (700 μmol mol−1 CO2) at two irradiances (150 and 500 μmol m−2 s−1) for 35 days at which point the plants were harvested. Elevated CO2 did not modify relative growth rate or biomass at either irradiance. Foliar carbon-to-nitrogen ratios were decreased at elevated CO2 and plants had a greater number of shorter tillers, particularly at the lower growth irradiance. Both light-limited and light-saturated rates of photosynthesis were stimulated. The amount of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) protein was increased at elevated CO2, but maximum extractable Rubisco activities were not significantly increased. A pronounced decrease in the Rubisco activation state was found with CO2 enrichment, particularly at the higher growth irradiance. Elevated-CO2-induced changes in leaf carbohydrate composition were small in comparison to those caused by changes in irradiance. No CO2-dependent effects on fructan biosynthesis were observed. Leaf respiration rates were increased by 68% in plants grown with CO2 enrichment and low light. We conclude that high CO2 will only result in increased biomass if total light input favourably increases the photosynthesis-to-respiration ratio. At low irradiances, biomass is more limited by increased rates of respiration than by CO2-induced enhancement of photosynthesis.
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    URL: http://dx.doi.org/10.1007/s004250050659
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    Mechanisms of inorganic carbon acquisition in Gracilaria gaditana nom. prov. (Rhodophyta) (1999)
    Springer
    Planta 208 (1999), S. 564-573 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Anion exchanger ; Carbonic anhydrase ; Gracilaria ; Inorganic carbon uptake ; pH-drift ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The mechanisms for acquisition of dissolved inorganic carbon (DIC) in the red macroalga Gracilaria gaditana nom. prov. have been investigated. The capacity for HCO3 − use by an extracellular carbonic anhydrase (CA; EC 4.2.1.1), and by an anion exchanger with similar properties to that of red blood cells (AE1), has been quantified. It was illustrated by comparing O2 evolution rates with those theoretically supported by CO2, as well as by photosynthesis-pH curves. Both external and internal CA, and a direct uptake were involved in HCO3 − use, since photosynthesis and pH evolution were affected by acetazolamide, 6-ethoxyzolamide (inhibitors of external and total CA, respectively) and 4,4′-diisothiocyanatostilbene-2,2′-disulfonate, (DIDS; an inhibitor of HCO3 − exchanger protein). The activity of the external CA was detected by a potentiometric method and by an alternative method based on the study of O2 evolution after addition of CO2 and acetazolamide. The latter method showed a residual photosynthetic rate due to direct HCO3 − use. Inhibitors caused a reduction in the pH compensation points in pH-drift experiments. The CO2 compensation points for photosynthesis increased when the inhibitors were applied, indicating a suppresion of the pathways involved in the carbon-concentrating mechanism. The net photosynthesis rates as a function of DIC concentration displayed a biphasic pattern that could be supported by the occurrence of the two mechanisms of HCO3 − use. The potential contribution to HCO3 − acquisition by the DIDS-sensitive mechanism was higher after culturing at a high pH. Our results suggest that the HCO3 − use by Gracilaria gaditana is carried out by the two DIC uptake mechanisms. These operate simultaneously with different affinities for DIC, the indirect HCO3 − use by an external CA activity being the main pathway. The presence of a carbon-concentrating mechanism confers eco-physiological advantages in a fluctuating ecosystem subjected daily to high pHs and low DIC concentrations.
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    URL: http://dx.doi.org/10.1007/s004250050594
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    Acclimation of Arabidopsis thaliana to the light environment: the role of photoreceptors (1999)
    Springer
    Planta 209 (1999), S. 517-527 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Acclimation ; Arabidopsis (acclimation) ; Chloroplast ; Photomorphogenesis ; Photoreceptor ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The regulation by light of the composition of the photosynthetic apparatus was investigated in photomorphogenic mutants of Arabidopsis thaliana (L.) Heynh. cv. Landsberg erecta. Leaf chlorophyll, photosynthesis, photosystem II function, and ribulose-1,5-bisphosphate carboxylase-oxygenase and photosystem II contents were determined for plants grown under high- or low-irradiance growth regimes. Although certain mutant lines had altered chloroplast composition compared to the wild type, all photoreceptor mutants tested were capable of light-dependent changes in chloroplast composition and photosynthetic function, indicating that photoreceptors do not play a central role in the regulation of acclimation at the level of the chloroplast. However, the clear acclimation defect in a det1 signal transduction mutant indicates that photoreceptor-controlled responses either share regulatory components with acclimation, or are important in the expression of components which in turn regulate acclimation. We suggest that the COP/DET/FUS regulatory cluster is a focus for multiple signal transduction pathways, including some of the metabolic signals which form the basis for the acclimatory response.
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    URL: http://dx.doi.org/10.1007/s004250050756
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    A preliminary study of the responsiveness to seasonal atmospheric and rainfall patterns of wash woodland species in the arid Richtersveld (1999)
    Springer
    Plant ecology 142 (1999), S. 141-160 
    Details
    ISSN: 1573-5052
    Keywords: Photosynthesis ; Phreatophyte ; Stable carbon isotope composition ; Water relations ; Winter rainfall desert
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seasonal carbon and water relations were compared among seven tree or shrub wash woodland species in the winter rainfall desert of the Richtersveld National Park, South Africa. Plants were generally aseasonal with respect to gas exchange, but responsive to rainfall events with respect to water relations and phenology. Relatively narrow annual ranges in potential evapotranspiration due to the maritime influence could explain why these plants respond more to fluctuations in water acquisition potential than to evaporative demand. Two species were summer-deciduous, but one of them (Ozoroa concolor) responded to aseasonal summer rainfall by leafing out and flowering. These two species had high shoot xylem water potentials when in leaf. All other species were sclerophyllous evergreens with low water potentials, particularly the shallow-rooted shrub Zygophyllum prismatocarpum, and Boscia albitrunca which may have a different rooting pattern to the other phreatophytes. The latter species was also unique due to its high leaf nitrogen contents, photosynthetic rates and stomatal conductances, despite very low leaf water potentials. Leaf stable carbon isotope composition C13δC) varied between species (−22 to −27‰), but was lower than the mean for arid regions worldwide. The values indicated moderately high levels of water use efficiency, but a less conservative strategy in two species, including Boscia albitrunca. The affinities of these species to summer rainfall biomes, their apparent decline in the western arid regions in recent geological history following aridification, and their absence southwards in the winter rainfall regions, suggest that these wash species rely on sporadic summer rainfall events to some extent. They may be at risk if predicted increases in temperature and changes in rainfall patterns alter their effective moisture availability.
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    URL: http://dx.doi.org/10.1023/A:1009882530364
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    Kinetic Mechanisms of Biological Regulation in Photosynthetic Organisms (1999)
    Springer
    Journal of biological physics 25 (1999), S. 177-192 
    Details
    ISSN: 1573-0689
    Keywords: Regulation ; Photosynthesis ; Fluorescence induction curve ; Modeling ; Primary photosynthetic reactions ; Calvin cycle ; Transmembraneelectric potential difference
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Principles of regulation on different levels of photosynthetic apparatus are discussed. Mathematical models of isolated photosynthetic reaction centers and general system of energy transduction in chloroplast are developed. A general approach to model these complex metabolic systems is suggested. Regulatory mechanisms in plant cell are correlated with the different patterns of fluorescence induction curve at different internal physiological states of the cells and external (environmental) conditions. Light regulation inside photosynthetic reaction centers, diffusion processes in thylakoid membrane, generation of transmembrane electrochemical potential, coupling with processes of CO2 fixation in Calvin Cycle are considered as stages of control of energy transformation in chloroplasts in their connection with kinetic patterns of fluorescence induction curves and other spectrophotometric data.
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    Acclimation to changing light conditions of long-term shade-grown beech (Fagus sylvatica L.) seedlings of different geographic origins (1998)
    Springer
    Trees 12 (1998), S. 326-333 
    Details
    ISSN: 0931-1890
    Keywords: Key words Fagus sylvatica ; Light acclimation ; Photoinhibition ; Photosynthesis ; Population
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Effects of changing light conditions on the ecophysiological condition behind survival were examined on beech from two different populations. Plants were grown in a greenhouse under simulated understorey and canopy gap light conditions. Upon exposure to high light maximum photosynthesis of shade-acclimated leaves increased followed by a reduction over several days to between high- and low-light control rates. In the reciprocal transfer, the decrease in maximum photosynthesis was rapid during the first 2–3 days and then levelled off to values comparable to low-light controls. Seedlings from Sicily (Madonie) showed generally higher maximum photosynthetic rates than those from Abetone. Leaf conductance varied in the same direction as photosynthesis in high- to low-light seedlings but to a lesser degree. Leaves grown under low light and exposed to high light experienced photoinhibition. The Abetone population was more susceptible to photoinhibitory damage than the seedlings from Sicily. Exposure to high light of shade-acclimated seedlings resulted in intermediate chlorophyll concentrations between levels of the high-light and low-light seedlings. Carotenoid concentration was unaffected by treatments. Seedlings grew more in high light, but had a lower leaf area ratio. Light-limited seedlings showed a shift in carbon allocation to foliage. Leaves formed in the new light regime maintained the same anatomy that had been developed before transfer. Seedlings from Sicily had thicker leaves than those of seedlings from Abetone. Seedlings from Abetone were found to be more susceptible to changing light conditions than seedlings from Sicily. We conclude that small forest gaps may represent a favorable environment for photosynthesis and growth of beech regeneration as a result of the limited ability of seedlings to acclimate to sudden increases in high irradiance and because of the moderate levels of light stress in small gaps.
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    URL: http://dx.doi.org/10.1007/PL00009719
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    Increase in the CO2 exchange rate of leaves of Ilex rotunda with elevated atmospheric CO2 concentration in an urban canyon (1998)
    Springer
    International journal of biometeorology 42 (1998), S. 16-21 
    Details
    ISSN: 1432-1254
    Keywords: Key words Carbon dioxide ; Photosynthesis ; Street tree ; Simulation model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Abstract  It was found that the atmospheric carbon dioxide (CO2) concentration in an urban canyon in Fukuoka city, Japan during August 1997 was about 30 µmol mol−1 higher than that in the suburbs. When fully exposed to sunlight, in situ the rate of photosynthesis in single leaves of Ilex rotunda planted in the urban canyon was higher when the atmospheric CO2 concentration was elevated. A biochemically based model was able to predict the in situ rate of photosynthesis well. The model also predicted an increase in the daily CO2 exchange rate for leaves in the urban canyon with an increase in atmospheric CO2 concentration. However, in situ such an increase in the daily CO2 exchange rate may be offset by diminished sunlight, a higher air temperature and a lower relative humidity. Thus, the daily CO2 exchange rate predicted using the model based soleley on the environmental conditions prevailing in the urban canyon was lower than that predicted based only on environmental factors found in the suburbs.
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    URL: http://dx.doi.org/10.1007/s004840050078
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    The functional ecology of shoot architecture in sun and shade plants of Heteromeles arbutifolia M. Roem., a Californian chaparral shrub (1998)
    Springer
    Oecologia 114 (1998), S. 1-10 
    Details
    ISSN: 1432-1939
    Keywords: Key words Functional plant architecture ; Heteromeles arbutifolia ; Light harvesting ; Phenotypic plasticity ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The functional roles of the contrasting morphologies of sun and shade shoots of the evergreen shrub Heteromeles arbutifolia were investigated in chaparral and understory habitats by applying a three-dimensional plant architecture simulation model, YPLANT. The simulations were shown to accurately predict the measured frequency distribution of photosynthetic photon flux density (PFD) on both the leaves and a horizontal surface in the open, and gave reasonably good agreement for the more complex light environment in the shade. The sun shoot architecture was orthotropic and characterized by steeply inclined (mean = 71o) leaves in a spiral phyllotaxy with short internodes. This architecture resulted in relatively low light absorption efficiencies (E A) for both diffuse and direct PFD, especially during the summer when solar elevation angles were high. Shade shoots were more plagiotropic with longer internodes and a pseudo-distichous phyllotaxis caused by bending of the petioles that positioned the leaves in a nearly horizontal plane (mean = 5o). This shade-shoot architecture resulted in higher E A values for both direct and diffuse PFD as compared to those of the sun shoots. Differences in E A between sun and shade shoots and between summer and winter were related to differences in projection efficiencies as determined by leaf and solar angles, and by differences in self shading resulting from leaf overlap. The leaves exhibited photosynthetic acclimation to the sun and the shade, with the sun leaves having higher photosynthetic capacities per unit area, higher leaf mass per unit area and lower respiration rates per unit area than shade leaves. Despite having 7 times greater available PFD, sun shoots absorbed only 3 times more and had daily carbon gains only double of those of shade shoots. Simulations showed that sun and shade plants performed similarly in the open light environment, but that shade shoots substantially outperformed sun shoots in the shade light environment. The shoot architecture observed in sun plants appears to achieve an efficient compromise between maximizing carbon gain while minimizing the time that the leaf surfaces are exposed to PFDs in excess of those required for light saturation of photosynthesis and therefore potentially photoinhibitory.
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    URL: http://dx.doi.org/10.1007/s004420050413
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    Growth, biomass allocation and photosynthesis of invasive and native Hawaiian rainforest species (1998)
    Springer
    Oecologia 117 (1998), S. 449-459 
    Details
    ISSN: 1432-1939
    Keywords: Key words Invasive species ; Photosynthesis ; Biomass allocation ; Hawaii ; Tropical rain forests
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Growth, biomass allocation, and photosynthetic characteristics of seedlings of five invasive non-indigenous and four native species grown under different light regimes were studied to help explain the success of invasive species in Hawaiian rainforests. Plants were grown under three greenhouse light levels representative of those found in the center and edge of gaps and in the understory of Hawaiian rainforests, and under an additional treatment with unaltered shade. Relative growth rates (RGRs) of invasive species grown in sun and partial shade were significantly higher than those for native species, averaging 0.25 and 0.17 g g−1 week−1, respectively, while native species averaged only 0.09 and 0.06 g g−1 week−1, respectively. The RGR of invasive species under the shade treatment was 40% higher than that of native species. Leaf area ratios (LARs) of sun and partial-shade-grown invasive and native species were similar but the LAR of invasive species in the shade was, on average, 20% higher than that of native species. There were no differences between invasive and native species in biomass allocation to shoots and roots, or in leaf mass per area across light environments. Light-saturated photosynthetic rates (Pmax) were higher for invasive species than for native species in all light treatments. Pmax of invasive species grown in the sun treatment, for example, ranged from 5.5 to 11.9 μmol m−2 s−1 as compared with 3.0−4.5 μmol m−2 s−1 for native species grown under similar light conditions. The slope of the linear relationship between Pmax and dark respiration was steeper for invasive than for native species, indicating that invasive species assimilate more CO2 at a lower respiratory cost than native species. These results suggest that the invasive species may have higher growth rates than the native species as a consequence of higher photosynthetic capacities under sun and partial shade, lower dark respiration under all light treatments, and higher LARs when growing under shade conditions. Overall, invasive species appear to be better suited than native species to capturing and utilizing light resources, particularly in high-light environments such as those characterized by relatively high levels of disturbance.
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    URL: http://dx.doi.org/10.1007/s004420050680
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    Is leaf-level photosynthesis related to plant success in a highly productive grassland? (1998)
    Springer
    Oecologia 117 (1998), S. 40-46 
    Details
    ISSN: 1432-1939
    Keywords: Key words Competition ; Grassland ; Photosynthesis ; Plant cover ; Tallgrass prairie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We addressed the question: “Are short-term, leaf-level measurements of photosynthesis correlated with long-term patterns of plant success?” in a productive grassland where interspecific competitive interactions are important. To answer this question, seasonal patterns of leaf-level photosynthesis were measured in 27 tallgrass prairie species growing in sites that differed in species composition and productivity due to differences in fire history. Our specific goals were to assess the relationship between gas exchange under field conditions and success (defined as aerial plant cover) for a wide range of species, as well as for these species grouped as dominant and sub-dominant grasses, forbs, and woody plants. Because fire increases productivity and dominance by grasses in this system, we hypothesized that any relationship between photosynthesis and success would be strongest in annually burned sites. We also predicted that regardless of fire history, the dominant species (primarily C4 grasses) would have higher photosynthetic rates than the less successful species (primarily C3 grasses, forbs and woody plants). Because forbs and woody species are less abundant in annually burned sites, we expected that these species would have lower photosynthetic rates in annually burned than in infrequently burned sites. As expected, the dominant C4␣grasses had the highest cover on all sites, relative to␣other growth forms, and they had the highest maximum and seasonally averaged photosynthetic rates (17.6 ± 0.42 μmol m−2 s−1). Woody species had the lowest average cover as well as the lowest average photosynthetic rates, with subdominant grasses and forbs intermediate in both cover and photosynthesis. Also as predicted, the highest overall photosynthetic rates were found on the most productive annually burned site. Perhaps most importantly, a positive relationship was found between leaf-level photosynthesis and cover for a core group of species when data were combined across all sites. These data support the hypothesis that higher instantaneous rates of leaf-level photosynthesis are indicative of long-term plant success in this grassland. However, in contrast to our predictions, the subdominant grasses, forbs and woody species on the annually burned site had higher photosynthetic rates than in the less frequently burned sites, even though their average cover was lower on annually burned sites, and hence they were less successful. The direct negative effect of fire on plant cover and species-specific differences in the availability of resources may explain why photosynthesis was high but cover was low in some growth forms in annually burned sites.
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    URL: http://dx.doi.org/10.1007/s004420050629
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    Cold hardening reduces photoinhibition of Eucalypts nitens and E. pauciflora at frost temperatures (1998)
    Springer
    Oecologia 113 (1998), S. 350-359 
    Details
    ISSN: 1432-1939
    Keywords: Key words Photoinhibition ; Photosynthesis ; Eucalypts ; Cold hardening ; Low temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photoinhibition of photosynthesis at low temperatures was investigated in two species of subalpine eucalypt, Eucalypts nitens (Deane and Maiden) Maiden and E. pauciflora Sieb. ex Spreng. Imposition of an artificial cold-hardening treatment increased the frost tolerance of leaf tissue and increased tolerance to excess light. Cold-hardened seedlings of both species had a higher photosynthetic capacity than non-hardened seedlings at 6 and 16°C and lower levels of non-photochemical quenching (NPQ) at 20 and 5°C. Furthermore, hardened seedlings had faster rates of NPQ development at 5 and −3.5°C. An increase in minimal fluorescence, which indicates slowly reversible photoinhibition, was evident in all seedlings at −1.5 and −3.5°C but was less pronounced in hardened seedlings, with a threefold faster rate of development of NPQ, at −3.5°C than non-hardened seedlings. Hardened seedlings also recovered faster from photoinhibition at −3.5°C. Thus cold hardening increased tolerance to high light in these species. Differences between E. nitens and E. pauciflora in their response to excess light were small and significant only at −3.5°C. Faster recovery from photoinhibition of E. pauciflora was consistent with its occurrence in colder habitats than E. nitens.
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    URL: http://dx.doi.org/10.1007/s004420050386
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    Contribution of photosynthetic rate to growth and reproduction in Amaranthus hybridus (1998)
    Springer
    Oecologia 117 (1998), S. 323-330 
    Details
    ISSN: 1432-1939
    Keywords: Key words Atrazine ; Resistance ; Fitness ; Path analysis ; Photosynthesis ; Selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract While it is known that genetic variation for photosynthetic and growth traits exists in natural populations, the functional significance of this variation remains unclear, particularly for photosynthetic traits. To test the hypothesis that photosynthetic rate has direct effects on reproduction as well as contributing indirectly to reproduction through effects on growth, we compared wild-type Amaranthus hybridus families to those with a single gene mutation that confers a lower photosynthetic rate. Wild-type and photosynthetic-mutant families were grown in competitive and non-competitive environments and we compared size, biomass allocation, architecture, and reproduction at three developmental stages. To assess the contributions of individual growth traits to reproduction, we calculated covariances between standardized traits and relative fitness (selection differentials), and compared selection between the two biotypes. Finally, we used path analysis to calculate the indirect effects of photosynthetic rate on fitness through growth. The size, allocation, and architecture of photosynthetic mutants did not differ from those of the wild type in either the competitive or non-competitive environment, with the exception that they were taller by the last developmental stage. However, the reproductive biomass of the photosynthetic mutants was significantly reduced compared to the wild type. In the competitive environment, the wild type achieved greater fitness because, while similar in size to the mutants, at any given size it produced more reproductive biomass. This suggests that photosynthetic rate affected the linkage between plant size and reproduction and is evidence of an indirect contribution to fitness. In the non-competitive environment, there were fewer differences in selection differentials between the two plant genotypes, suggesting fewer indirect effects. Path analysis showed that variation in photosynthetic biotype had indirect effects on reproductive biomass, via growth traits, and that there were no direct effects. Photosynthetic rate appears to have fitness consequences primarily through multiple contributions to growth throughout development.
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    URL: http://dx.doi.org/10.1007/s004420050665
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    Photosynthetic responses of Microstegium vimineum (Trin.) A. Camus, a shade-tolerant, C4 grass, to variable light environments (1998)
    Springer
    Oecologia 114 (1998), S. 11-19 
    Details
    ISSN: 1432-1939
    Keywords: Key wordsMicrostegium vimineum ; Sunflecks ; Photosynthesis ; Induction ; C4 pathway
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Microstegium vimineum (Trin.) A. Camus, a shade-tolerant C4 grass, has spread throughout the eastern United States since its introduction in 1919. This species invades disturbed understory habitats along streambanks and surrounding mesic forests, and has become a major pest in areas such as Great Smoky Mountains National Park. The focus of this study was to characterize the photosynthetic induction responses of M. vimineum, specifically its ability to utilize low light and sunflecks, two factors that may be critical to invasive abilities and survival in the understory. In addition, we were curious about the ability of a grass with the C4 photosynthetic pathway to respond to sunflecks. Plants were grown under 25% and 50% ambient sunlight, and photosynthetic responses to both steady-state and variable light were determined. Plants grown in both 25% and 50% ambient sun became 90% light saturated between 750–850 μmol m−2 s−1; however, plants grown in 50% ambient sun had significantly higher maximum steady-state photosynthetic rates (16.09 ± 1.37 μmol m−2 s−1 vs. 12.71 ± 1.18 μmol m−2 s−1). Both groups of plants induced to 50% of the steady-state rate in 3–5 min, while it took 10–13 min to reach 90% of maximum rates, under both flashing and steady-state light. For both groups of plants, stomatal conductance during induction reached maximum rates in 6–7 min, after which rates decreased slightly. Upon return to low light, rates of induction loss and stomatal closure were very rapid in both groups of plants, but were more rapid in those grown in high light. Rapid induction and the ability to induce under flashing light may enable this species to invade and dominate mesic understory habitats, while rapid induction loss due to stomatal closure may prevent excess water loss when low light constrains photosynthesis. The C4 pathway itself does not appear to present an insurmountable barrier to the ability of this grass species to respond to sunflecks in an understory environment.
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    URL: http://dx.doi.org/10.1007/s004420050414
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    Photosynthetic nitrogen-use efficiency of species that differ inherently in specific leaf area (1998)
    Springer
    Oecologia 116 (1998), S. 26-37 
    Details
    ISSN: 1432-1939
    Keywords: Key words Interspecific variation ; Nitrogen ; Photosynthesis ; Photosynthetic nitrogen use efficiency ; Specific leaf area
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Factors that contribute to interspecific variation in photosynthetic nitrogen-use efficiency (PNUE, the ratio of CO2 assimilation rate to leaf organic nitrogen content) were investigated, comparing ten dicotyledonous species that differ inherently in specific leaf area (SLA, leaf area:leaf dry mass). Plants were grown hydroponically in controlled environment cabinets at two irradiances (200 and 1000 μmol m–2 s–1). CO2 and irradiance response curves of photosynthesis were measured followed by analysis of the chlorophyll, Rubisco, nitrate and total nitrogen contents of the leaves. At both irradiances, SLA ranged more than twofold across species. High-SLA species had higher in situ rates of photosynthesis per unit leaf mass, but similar rates on an area basis. The organic N content per unit leaf area was lower for the high-SLA species and consequently PNUE at ambient light conditions (PNUEamb) was higher in those plants. Differences were somewhat smaller, but still present, when PNUE was determined at saturating irradiances (PNUEmax). An assessment was made of the relative importance of the various factors that underlay interspecific variation in PNUE. For plants grown under low irradiance, PNUEamb of high-SLA species was higher primarily due to their lower N content per unit leaf area. Low-SLA species clearly had an overinvestment in photosynthetic N under these conditions. In addition, high SLA-species allocated a larger fraction of organic nitrogen to thylakoids and Rubisco, which further increased PNUEamb. High-SLA species grown under high irradiance showed higher PNUEamb mainly due to a higher Rubisco specific activity. Other factors that contributed were again their lower contents of Norg per unit leaf area and a higher fraction of photosynthetic N in electron transport and Rubisco. For PNUEmax, differences between species in organic leaf nitrogen content per se were no longer important and higher PNUEmax of the high SLA species was due to a higher fraction of N in␣photosynthetic compounds (for low-light plants) and a higher Rubisco specific activity (for high-light grown plants).
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    URL: http://dx.doi.org/10.1007/s004420050560
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    The significance of thallus size for the water economy of the cyanobacterial old-forest lichen Degelia plumbea (1998)
    Springer
    Oecologia 116 (1998), S. 76-84 
    Details
    ISSN: 1432-1939
    Keywords: Key words Epiphytic lichens ; Hypothallus ; Photosynthesis ; Water loss ; Water-holding capacity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Rosette-formed, circular thalli of Degelia plumbea were studied in the laboratory. Regardless of thallus size, the optimal quantum yield of photosystem II (F V/F M) remained at a high, constant level during a drying cycle starting with fully hydrated thalli until the thallus water content reached about 200%. Net photosynthesis reached a maximum level at this hydration level. Thereafter, both F V/F M and net photosynthesis fell rapidly to zero at a water content of somewhat less than 100%. There was a highly significant, positive relationship between thallus size and the water-holding capacity, as well as a strong, negative correlation between size and water loss per thallus area. Consequently, an increase in thallus size from 1 to 36 cm2 lead to a tenfold prolongation of the photosynthetically active period during a drying cycle at a low radiation regime. The improved water-holding capacity in larger thalli is mainly a result of a thicker hypothallus. The fast desiccation of small thalli suggests that the regeneration of D. plumbea could be severely hampered by nearby logging that raises the evaporative demand by increasing radiation loads and wind exposure at remaining lichen sites.
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    URL: http://dx.doi.org/10.1007/s004420050565
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    Physiological and morphological variation in Metrosideros polymorpha, a dominant Hawaiian tree species, along an altitudinal gradient: the role of phenotypic plasticity (1998)
    Springer
    Oecologia 113 (1998), S. 188-196 
    Details
    ISSN: 1432-1939
    Keywords: Key wordsMetrosideros polymorpha ; Phenotypic plasticity ; Photosynthesis ; Carbon isotope ratios ; Photosynthetic nitrogen use efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Metrosideros polymorpha, a dominant tree species in Hawaiian ecosystems, occupies a wide range of habitats. Complementary field and common-garden studies of M. polymorpha populations were conducted across an altitudinal gradient at two different substrate ages to ascertain if the large phenotypic variation of this species is determined by genetic differences or by phenotypic modifications resulting from environmental conditions. Several characteristics, including ecophysiological behavior and anatomical features, were largely induced by the environment. However, other characteristics, particularly leaf morphology, appeared to be mainly determined by genetic background. Common garden plants exhibited higher average rates of net assimilation (5.8 μmol CO2 m−2 s−1) and higher average stomatal conductance (0.18 mol H2O m−2 s−1) than their field counterparts (3.0 μmol CO2 m−2 s−1, and 0.13 mol H2O m−2 s−1 respectively). Foliar δ13C of most common-garden plants was similar among sites of origin with an average value of −26.9‰. In contrast, mean values of foliar δ13C in field plants increased substantially from −29.5‰ at low elevation to −24.8‰ at high elevation. Leaf mass per unit area increased significantly as a function of elevation in both field and common garden plants; however, the range of values was much narrower in common garden plants (211–308 g m−2 for common garden versus 107–407 g m−2 for field plants). Nitrogen content measured on a leaf area basis in common garden plants ranged from 1.4 g m−2 to 2.4 g m−2 and from 0.8 g m−2 to 2.5 g m−2 in field plants. Photosynthetic nitrogen use efficiency (PNUE) decreased 50% with increasing elevation in field plants and only 20% in plants from young substrates in the common garden. This was a result of higher rates of net CO2 assimilation in the common garden plants. Leaf tissue and cell layer thickness, and degree of leaf pubescence increased significantly with elevation in field plants, whereas in common garden plants, variation with elevation of origin was much narrower, or was entirely absent. Morphological characteristics such as leaf size, petiole length, and internode length decreased with increasing elevation in the field and were retained when grown in the common garden, suggesting a potential genetic basis for these traits. The combination of environmentally induced variability in physiological and anatomical characteristics and genetically determined variation in morphological traits allows Hawaiian M. polymorpha to attain and dominate an extremely wide ecological distribution not observed in other tree species.
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    URL: http://dx.doi.org/10.1007/s004420050367
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    Intraspecific variation in photosynthetic responses of trebouxioid lichens with reference to the activity of a carbon-concentrating mechanism (1998)
    Springer
    Oecologia 113 (1998), S. 360-369 
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    ISSN: 1432-1939
    Keywords: Key words Lichen ; Phycobiont ; Photosynthesis ; Carbon-concentrating mechanism ; Carbon isotope discrimination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The photosynthetic responses of a range of trebouxioid lichens were investigated to determine whether variations in net assimilation rates shown by populations of the same species collected from different habitats could be correlated with adjustments in carbon-concentrating mechanism (CCM) activity. The activity of a CCM was inferred from the high affinity for CO2 [i.e. low CO2 compensation point (Γ); low external CO2 concentration at which half-maximal assimilation rates are reached (K 0.5 CO2)], the release of a pool of accumulated dissolved inorganic carbon (Ci) during light/dark transient measurements of CO2 exchange and values for carbon isotope discrimination intermediate between those characteristic of C3 and C4 terrestrial plants. Higher net and gross assimilation rates were expressed by lichens collected from shaded woodland habitats. The higher rates were not accounted for by variations in chlorophyll content. Lichens with high assimilation rates also showed an increased affinity for CO2 as demonstrated by low CO2 compensation points and K 0.5 values and the magnitude of the Ci pool accumulated upon illumination and released after darkening of the thalli. However, there was no correlation between assimilation rates and organic matter or instantaneous carbon isotope discrimination measurements, with the latter remaining roughly consistent whatever the provenance or species of the lichen material. The data are discussed with reference to significant environmental factors which are likely to control photosynthesis in the habitats studied.
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    URL: http://dx.doi.org/10.1007/s004420050387
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    The impact of two gall-forming arthropods on the photosynthetic rates of their hosts (1998)
    Springer
    Oecologia 115 (1998), S. 161-166 
    Details
    ISSN: 1432-1939
    Keywords: Key words Galls ; Photosynthesis ; Herbivory ; Eriophyid ; Aphid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The impact of herbivores on host plant photosynthetic rates can range from negative to positive. While defoliation by chewing herbivores can result in increases in photosynthesis followed by compensatory growth, other herbivore guilds, such as mesophyll feeders which damage photosynthetic leaf tissues, almost always reduce photosynthetic rates. The impact of galling herbivores on host photosynthesis has rarely been examined, even though the limited tissue disruption and the strong metabolic sinks induced by gall-forming herbivores could potentially stimulate photosynthetic rates. I examined the hypothesis that gall-inducing herbivores could stimulate photosynthesis in neighboring leaves in response to increased sink-demand by the gall. To address this hypothesis, I measured photosynthetic rates of galled leaves or leaflets, neighboring ungalled leaves or leaflets, and ungalled leaves or leaflets on ungalled shoots on naturally growing Prunus serotina (wild cherry) and Rhus glabra (smooth sumac). The leaves of wild cherry were galled by an eriophyid mite, Phytoptus cerasicrumena; the leaves of smooth sumac by an aphid, Melaphis rhois. I found that both species reduced the photosynthetic rates of the leaves or leaflets they galled from 24 to 52% compared to ungalled leaves in ungalled areas of the plants. Contrary to my hypothesis, mite galls on wild cherry reduced photosynthesis of neighboring ungalled leaves within the same shoot by 24% compared to ungalled leaves on gall-free shoots. Aphid galls on sumac leaflets did not significantly alter the photosynthetic rates of neighboring leaflets relative to ungalled leaves on ungalled shoots. Although gall-formers would appear to have the potential to stimulate photosynthesis in the same manner as defoliating herbivores, i.e., by increasing sink demand relative to source supply, I found only negative impacts on photosynthesis. I suggest that sink competition for nutrients between developing leaves and growing gall tissue may account for the negative impacts of sink-inducing gallers on photosynthesis.
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    URL: http://dx.doi.org/10.1007/s004420050503
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    A 38-kilodalton low-CO2-inducible polypeptide is associated with the pyrenoid in Chlorella vulgaris (1998)
    Springer
    Planta 206 (1998), S. 416-425 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Carbonic anhydrase ; Chlorella ; CO2-concentrating mechanism ; Photosynthesis ; Pyrenoid ; Ribulose-1 ; 5-bisphosphate carboxylase/oxygenase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. In the green alga Chlorella vulgaris UAM 101, a CO2-concentrating mechanism (CCM) is induced when cells are transferred from high (5%) to low (0.03%) CO2 concentrations. The induction of the CCM is correlated with de-novo synthesis of several polypeptides that remain to be identified. The internal carbonic anhydrase (CA; EC 4.2.1.1) activity increased 6- to 7-fold within 6 h of acclimation to air. When crude homogenates were further separated into soluble and insoluble fractions, nearly all of the CA activity was associated with the membrane fraction. Immunoblot analysis of cell homogenates probed with antibodies raised against the 37-kDa subunit of periplasmic CA of Chlamydomonas reinhardtii showed a cross-reaction with a single 38-kDa polypeptide in both high- and low-CO2-grown cells. The up-regulation of the expression of the 38-kDa polypeptide was closely correlated with the increase in internal CA activity. Furthermore, its subcellular location was also correlated with the distribution of the activity. Immunoblot analysis of pyrenoid fractions showed that the 38-kDa polypeptide was concentrated in the pyrenoids from low-CO2-grown cells but was not present in pyrenoids from high-CO2-grown cells. In addition, immunogold labeling experiments showed that the protein was mainly associated with membranes crossing the pyrenoid, while it was absent from the pyrenoid matrix. These studies have identified a putative intracellular CA polypeptide associated with the pyrenoid in Chlorella vulgaris, suggesting that this structure may play an important role in the operation of the CCM and the acclimation to low CO2 conditions.
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    URL: http://dx.doi.org/10.1007/s004250050417
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