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  • 1
    Electronic Resource
    Electronic Resource
    15N natural abundance of vascular rainforest epiphytes: implications for nitrogen source and acquisition (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 18 (1995), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The foliar natural abundance of 15N was analysed to compare the potential nitrogen sources of vascular rainforest epiphytes and associated soil-rooted trees. Leaves of epiphytes collected from six rainforest communities in Brazil, Australia and the Solomon Islands were depleted in 15N relative to the trees at each site. Epiphyte δ15N was as low as -6.4%o, while trees were generally enriched in 15N (0.7 to 3.5%o). These results indicate either that epiphytes use nitrogen sources depleted in 15N or that discrimination against 15N is an intrinsic function of epiphyte physiology. At three sites, epiphytes could be grouped into those having both low δ15N and low leaf-nitrogen content and those possessing both high δ15N and high leaf-nitrogen content. The second group had δ15N values in the range sometimes attributable to N2 fixation (-2 to 0%o). There was no correlation between growth form and δ15N. It is concluded that epiphytes may utilize 15N-depleted nitrogen from atmospheric deposition and N2 fixation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1995.tb00547.x
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  • 2
    Electronic Resource
    Electronic Resource
    The relative impacts of daytime and night-time warming on photosynthetic capacity in Populus deltoides (2002)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 25 (2002), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: In order to investigate the relative impacts of increases in day and night temperature on tree carbon relations, we measured night-time respiration and daytime photosynthesis of leaves in canopies of 4-m-tall cottonwood (Populus deltoides Bartr. ex Marsh) trees experiencing three daytime temperatures (25, 28 or 31 °C) and either (i) a constant nocturnal temperature of 20 °C or (ii) increasing nocturnal temperatures (15, 20 or 25 °C). In the first (day warming only) experiment, rates of night-time leaf dark respiration (Rdark) remained constant and leaves displayed a modest increase (11%) in light-saturated photosynthetic capacity (Amax) during the day (1000–1300 h) over the 6 °C range. In the second (dual night and day warming) experiment, Rdark increased by 77% when nocturnal temperatures were increased from 15 °C (0·36 µmol m−2 s−1) to 25 °C (0·64 µmol m−2 s−1). Amax responded positively to the additional nocturnal warming, and increased by 38 and 64% in the 20/28 and 25/31 °C treatments, respectively, compared with the 15/25 °C treatment. These increases in photosynthetic capacity were associated with strong increases in the maximum carboxylation rate of rubisco (Vcmax) and ribulose-1,5-bisphosphate (RuBP) regeneration capacity mediated by maximum electron transport rate (Jmax). Leaf soluble sugar and starch concentration, measured at sunrise, declined significantly as nocturnal temperature increased. The nocturnal temperature manipulation resulted in a significant inverse relationship between Amax and pre-dawn leaf carbohydrate status. Independent measurements of the temperature response of photosynthesis indicated that the optimum temperature (Topt) acclimated fully to the 6 °C range of temperature imposed in the daytime warming. Our findings are consistent with the hypothesis that elevated night-time temperature increases photosynthetic capacity during the following light period through a respiratory-driven reduction in leaf carbohydrate concentration. These responses indicate that predicted increases in night-time minimum temperatures may have a significant influence on net plant carbon uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2002.00947.x
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  • 3
    Electronic Resource
    Electronic Resource
    The impact of mycorrhizal colonization upon nitrogen source utilization and metabolism in seedlings of Eucalyptus grandis Hill ex Maiden and Eucalyptus maculata Hook (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 18 (1995), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Analysis of soil solution from forest sites dominated by Eucalyptus grandis and Eucalyptus maculata indicates that soluble forms of organic nitrogen (amino acids and protein) are present in concentrations similar to those of mineral nitrogen (nitrate and ammonium). Experiments were conducted to determine the extent to which mycorrhizal associations might broaden nitrogen source utilization in Eucalyptus seedlings to include organic nitrogen. In isolation, species of ectomycorrhizal fungi from northern Australia show varying abilities to utilize mineral and organic forms of nitrogen as sole sources. Pisolithus sp. displayed strongest growth on NH4+, glutamine and asparagine, but grew poorly on protein, while Amanita sp. grew well both on mineral sources and on a range of organic sources (e.g. arginine, asparagine, glutamine and protein). In sterile culture, non-mycorrhizal seedlings of Eucalyptus grandis and Eucalyptus maculata grew well on mineral sources of nitrogen, but showed no ability to grow on sources of organic nitrogen other than glutamine. In contrast, mycorrhizal seedlings grew well on a range of organic nitrogen sources. These observations indicate that mycorrhizal associations confer on species of Eucalyptus the ability to broaden their resource base substantially with respect to nitrogen. This ability to utilize organic nitrogen was not directly related to that of the fungal symbiont in isolation. Seedlings mycorrhizal with Pisolithus sp. were able to assimilate sources of nitrogen (in particular histidine and protein) on which the fungus in pure culture appeared to grow weakly. Experiments in which plants were fed 15N-labelled ammonium were undertaken in order to investigate the influence of mycorrhizal colonization on the pathway of nitrogen metabolism. In roots and shoots of all seedlings, 15N was incorporated into the amide group of glutamine, and label was also found in the amino groups of glutamine, glutamic acid, γ-aminobutyric acid and alanine. Mycorrhizal colonization appeared to have no effect on the assimilation pathway and metabolism of [15N]H4+; labelling data were consistent with the operation of the glutamate synthase cycle in plants infected with either Pisolithus sp. (which in isolation assimilates via the glutamate synthase cycle) or Elaphomyces sp. (which assimilates via glutamate dehydrogenase). It is likely that the control of carbon supply to the mycorrhizal fungus from the host may have a profound effect on both the assimilatory pathway and the range of nitrogen sources that can be utilized by the association.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1995.tb00199.x
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  • 4
    Electronic Resource
    Electronic Resource
    The onset of photosynthetic acclimation to elevated CO2 partial pressure in field-grown Pinus radiata D. Don. after 4 years (2000)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 23 (2000), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effects of CO2 enrichment on photosynthesis and ribulose-1,5-bisphosphate carboxylase/oxygenase (rubisco) were studied in current year and 1-year-old needles of the same branch of field-grown Pinus radiata D. Don trees. All measurements were made in the fourth year of growth in large, open-top chambers continuously maintained at ambient (36 Pa) or elevated (65 Pa) CO2 partial pressures. Photosynthetic rates of the 1-year-old needles made at the growth CO2 partial pressure averaged 10·5 ± 0·5 μmol m−2 s−1 in the 36 Pa grown trees and 11·8 ± 0·4 μmol m−2 s−1 in the 65 Pa grown trees, and were not significantly different from each other. The photosynthetic capacity of 1-year-old needles was reduced by 25% from 23·0 ± 1·8 μmol m−2 s−1 in the 36 Pa CO2 grown trees to 17·3 ± 0·7 μmol m−2 s−1 in the 65 Pa grown trees. Growth in elevated CO2 also resulted in a 25% reduction in Vcmax (maximum carboxylation rate), a 23% reduction in Jmax (RuBP regeneration capacity mediated by maximum electron transport rate) and a 30% reduction in Rubisco activity and content. Total non-structural carbohydrates (TNC) as a fraction of total dry mass increased from 12·8 ± 0·4% in 1-year-old needles from the 36 Pa grown trees to 14·2 ± 0·7% in 1-year-old needles from the 65 Pa grown trees and leaf nitrogen content decreased from 1·30 ± 0·02 to 1·09 ± 0·10 g m−2. The current-year needles were not of sufficient size for gas exchange measurements, but none of the biochemical parameters measured (Rubisco, leaf chlorophyll, TNC and N), were effected by growth in elevated CO2. These results demonstrate that photosynthetic acclimation, which was not found in the first 2 years of this experiment, can develop over time in field-grown trees and may be regulated by source-sink balance, sugar feedback mechanisms and nitrogen allocation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2000.00622.x
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  • 5
    Electronic Resource
    Electronic Resource
    Photosynthetic acclimation to long-term exposure to elevated CO2 concentration in Pinus radiata D. Don. is related to age of needles (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 21 (1998), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The effects of CO2 enrichment on photosynthesis and ribulose-1,5-bisphosphate carboxylase/ oxygenase (Rubisco) in current year and 1-year-old needles on the same branch were studied on Pinus radiata D. Don. trees growing for 4 years in large, open-top chambers at ambient (36 Pa) and elevated (65 Pa) CO2 partial pressures. At this age trees were 3·5–4 m tall. Measurements made late in the growing cycle (March) showed that photosynthetic rates at the growth CO2 concentration [(pCO2)a] were lower in 1-year-old needles of trees grown at elevated CO2 concentrations than in those of trees grown at ambient (pCO2)a. At elevated CO2 concentrations Vcmax (maximum carboxylation rate) was reduced by 13% and Jmax (RuBP regeneration capacity mediated by maximum electron transport rate) by 17%. This corresponded with photosynthetic rates at the growth (pCO2)a of 4·68 ± 0·41 μmol m–2 s–1 and 6·15 ± 0·46 μmol m–2 s–1 at 36 and 65 Pa, respectively (an enhancement of 31%). In current year needles photosynthetic rates at the growth (pCO2)a were 6·2 ± 0·72 μmol m–2 s–1 at 36 Pa and 10·15 ± 0·64 μmol m–2 s–1 at 65 Pa (an enhancement of 63%). The smaller enhancement of photosynthesis in 1-year-old needles at 65 Pa was accompanied by a reduction in Rubisco activity (39%) and content (40%) compared with that at 36 Pa. Starch and sugar concentrations in 1-year-old needles were not significantly different in the CO2 treatments. There was no evidence in biochemical parameters for down-regulation at elevated (pCO2)a in fully fexpanded needles of the current year cohort. These data show that enhancement of photosynthesis continues to occur in needles after 4 years’ exposure to elevated CO2 concentrations. Photosynthetic acclimation reduces the degree of this enhancement, but only in needles after 1 year of growth. Thus, responses to elevated CO2 concentration change during the lifetime of needles, and acclimation may not be apparent in current year needles. This transitory effect is most probably attributable to the effects of developmental stage and proximity to actively growing shoots on sink strength for carbohydrates. The implications of such age-dependent responses are that older trees, in which the contribution of older needles to the photosynthetic biomass is greater than in younger trees, may become progressively more acclimated to elevated CO2 concentration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1998.00374.x
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  • 6
    Electronic Resource
    Electronic Resource
    Nitrogen relations of natural and disturbed plant communities in tropical Australia (1998)
    Springer
    Oecologia 117 (1998), S. 95-104 
    Details
    ISSN: 1432-1939
    Keywords: Key words Nitrate ; Nitrogen utilisation ; Tropical woodland ; Tropical monsoon forest ; Xylem sap
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen relations of natural and disturbed tropical plant communities in northern Australia (Kakadu National Park) were studied. Plant and soil N characteristics suggested that differences in N source utilisation occur at community and species level. Leaf and xylem sap N concentrations of plants in different communities were correlated with the availability of inorganic soil N (NH+ 4 and NO− 3). In general, rates of leaf NO− 3 assimilation were low. Even in communities with a higher N status, including deciduous monsoon forest, disturbed wetland, and a revegetated mine waste rock dump, levels of leaf nitrate reductase, xylem and leaf NO− 3 levels were considerably lower than those that have been reported for eutrophic communities. Although NO− 3 assimilation in escarpment and eucalypt woodlands, and wetland, was generally low, within these communities there was a suite of species that exhibited a greater capacity for NO− 3 assimilation. These “high- NO− 3 species” were mainly annuals, resprouting herbs or deciduous trees that had leaves with high N contents. Ficus, a high-NO− 3 species, was associated with soil exhibiting higher rates of net mineralisation and net nitrification. “Low-NO− 3 species” were evergreen perennials with low leaf N concentrations. A third group of plants, which assimilated NO− 3 (albeit at lower rates than the high-NO− 3 species), and had high-N leaves, were leguminous species. Acacia species, common in woodlands, had the highest leaf N contents of all woody species. Acacia species appeared to have the greatest potential to utilise the entire spectrum of available N sources. This versatility in N source utilisation may be important in relation to their high tissue N status and comparatively short life cycle. Differences in N utilisation are discussed in the context of species life strategies and mycorrhizal associations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050636
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  • 7
    Electronic Resource
    Electronic Resource
    The effect of light quantity and quality during development on the photosynthetic characteristics of six Australian rainforest tree species (1991)
    Springer
    Oecologia 87 (1991), S. 110-117 
    Details
    ISSN: 1432-1939
    Keywords: Rainforest ; Photosynthesis ; Dark respiration ; Growth irradiance ; R/FR ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Seedlings of six subtropical rainforest tree species representing early (Omalanthus populifolius, Solanum aviculare), middle (Duboisia myoporoides, Euodia micrococca) and late (Acmena ingens, Argyrodendron actinophyllum) successional stages in forest development were grown in a glasshouse, under four levels of neutral shade (60%, 15%, 5%, 1% of photosynthetically active radiation (PAR) in incident sunlight) and three levels of selectively filtered shade (producing 15%, 5%, 1% of PAR). This design served to analyse the interactions between reduced photon flux density (PFD) and reduced red/far-red (R/FR) ratio in their effects on selected photosynthetic characteristics of each species. The light-saturated rate of photosynthesis was significantly influenced by growth irradiance in five of the six species, with all of these showing a non-linear decrease in maximum assimilation rate from 60% down to 1% PAR. The degree of acclimation to this range was not clearly related to the successional status of the species. Dark respiration was more sensitive to growth irradiance in the early- and mid-stage species than in the late-stage species. Although levels of dark respiration were clearly greater in leaves of early- and mid-stage species from the highest light levels, differences between successional groups were negligible at 1% PAR. Growth in filtered shade, typical of that beneath a closed canopy, resulted in lower photosynthetic capacities and quantum yields in those species which did respond. Although dark respiration rates were more sensitive to filtered shade in the early-stage than in the late-stage species, there was no evidence from other gas exchange characteristics to suggest that overall sensitivity to light quality (as characterised by the R/FR ratio) is greater in early successional-stage species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00323788
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  • 8
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    Plant growth in elevated CO2 alters mitochondrial number and chloroplast fine structure (2001)
    National Academy of Sciences
    Details
    Publication Date: 2001-02-27
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 9
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    Temperature response of leaf respiration [Ecology] (2016)
    National Academy of Sciences
    Details
    Publication Date: 2016-04-06
    Description: Plant respiration constitutes a massive carbon flux to the atmosphere, and a major control on the evolution of the global carbon cycle. It therefore has the potential to modulate levels of climate change due to the human burning of fossil fuels. Neither current physiological nor terrestrial biosphere models adequately describe...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 10
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    Urban environment of New York City promotes growth in northern red oak seedlings (2012)
    Oxford University Press
    Details
    Publication Date: 2012-04-28
    Description: Urbanization is accelerating across the globe, elevating the importance of studying urban ecology. Urban environments exhibit several factors affecting plant growth and function, including high temperatures (particularly at night), CO 2 concentrations and atmospheric nitrogen deposition. We investigated the effects of urban environments on growth in Quercus rubra L. seedlings. We grew seedlings from acorns for one season at four sites along an urban–rural transect from Central Park in New York City to the Catskill Mountains in upstate New York (difference in average maximum temperatures of 2.4 °C; difference in minimum temperatures of 4.6 °C). In addition, we grew Q. rubra seedlings in growth cabinets (GCs) mimicking the seasonal differential between the city and rural sites (based on a 5-year average). In the field experiment, we found an eightfold increase in biomass in urban-grown seedlings relative to those grown at rural sites. This difference was primarily related to changes in growth allocation. Urban-grown seedlings and seedlings grown at urban temperatures in the GCs exhibited a lower root: shoot ratio (urban ~0.8, rural/remote ~1.5), reducing below-ground carbon costs associated with construction and maintenance. These urban seedlings instead allocated more growth to leaves than did rural-grown seedlings, resulting in 10-fold greater photosynthetic area but no difference in photosynthetic capacity of foliage per unit area. Seedlings grown at urban temperatures in both the field and GC experiments had higher leaf nitrogen concentrations per unit area than those grown at cooler temperatures (increases of 23% in field, 32% in GC). Lastly, we measured threefold greater 13 C enrichment of respired CO 2 (relative to substrate) in urban-grown leaves than at other sites, which may suggest greater allocation of respiratory function to growth over maintenance. It also shows that lack of differences in total R flux in response to environmental conditions may mask dramatic shifts in respiratory functioning. Overall, our findings indicating greater seedling growth and establishment at a critical regeneration phase of forest development may have important implications for the ecology of urban forests as well as the predicted growth of the terrestrial biosphere in temperate regions in response to climate change.
    Print ISSN: 0829-318X
    Electronic ISSN: 1758-4469
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Oxford University Press
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