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  • 1
    Electronic Resource
    Electronic Resource
    Effects of genotype and temperature on pollen tube growth in perennial ryegrass (Lolium perenne L.) (1989)
    Springer
    Sexual plant reproduction 2 (1989), S. 225-230 
    Details
    ISSN: 1432-2145
    Keywords: Lolium perenne ; Pollen tube ; Genotype ; Temperature ; Self-incompatibility ; Seed production
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Low yield in seed crops of perennial ryegrass is related to low fertilization efficiency and low temperature during anthesis. To study the effect of genotype and temperature on pollen performance, we conducted greenhouse experiments at controlled temperatures. Individual florets of four genotypes that are known to differ in seed production were hand pollinated at four temperatures (14°, 18°, 22°, 26° C) both in vivo and via a semiin-vitro method involving excised florets on agar. Pollen germination and tube growth were determined with UV-fluorescence microscopy and scored in six classes at 2 h after pollination in vitro and after 0.5, 2 and 5 h in vivo. In vitro, both genotype and temperature had a significant effect on the performance of self-pollen. Pollen tube growth increased with temperature. In cross-pollinations, the pistil parent had a significant effect on pollen tube growth, and there was also a significant pistil-by-temperature interaction. In vivo, genotype and temperature significantly affected pollen performance. The genotype-by-temperature interaction was only significant 5 h after pollination. One genotype with low seed yield was pseudoself-compatible and was a relatively poor mother after cross-pollination. The effects of genotype and temperature on the growth of self-pollen might be exploited in a breeding programme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00195583
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  • 2
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    Widespread increase of tree mortality rates in the western United States (2009)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2009-01-24
    Description: Persistent changes in tree mortality rates can alter forest structure, composition, and ecosystem services such as carbon sequestration. Our analyses of longitudinal data from unmanaged old forests in the western United States showed that background (noncatastrophic) mortality rates have increased rapidly in recent decades, with doubling periods ranging from 17 to 29 years among regions. Increases were also pervasive across elevations, tree sizes, dominant genera, and past fire histories. Forest density and basal area declined slightly, which suggests that increasing mortality was not caused by endogenous increases in competition. Because mortality increased in small trees, the overall increase in mortality rates cannot be attributed solely to aging of large trees. Regional warming and consequent increases in water deficits are likely contributors to the increases in tree mortality rates.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉van Mantgem, Phillip J -- Stephenson, Nathan L -- Byrne, John C -- Daniels, Lori D -- Franklin, Jerry F -- Fule, Peter Z -- Harmon, Mark E -- Larson, Andrew J -- Smith, Jeremy M -- Taylor, Alan H -- Veblen, Thomas T -- New York, N.Y. -- Science. 2009 Jan 23;323(5913):521-4. doi: 10.1126/science.1165000.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉U.S. Geological Survey, Western Ecological Research Center, Three Rivers, CA 93271, USA. pvanmantgem@usgs.gov〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19164752" target="_blank"〉PubMed〈/a〉
    Keywords: Abies/anatomy & histology/growth & development ; *Climate ; *Coniferophyta/anatomy & histology/growth & development ; *Ecosystem ; Fires ; Models, Statistical ; Nonlinear Dynamics ; Northwestern United States ; Pinus/anatomy & histology/growth & development ; Temperature ; *Trees/growth & development ; Tsuga/anatomy & histology/growth & development ; United States
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Rise and fall of the Beringian steppe bison (2004)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2004-11-30
    Description: The widespread extinctions of large mammals at the end of the Pleistocene epoch have often been attributed to the depredations of humans; here we present genetic evidence that questions this assumption. We used ancient DNA and Bayesian techniques to reconstruct a detailed genetic history of bison throughout the late Pleistocene and Holocene epochs. Our analyses depict a large diverse population living throughout Beringia until around 37,000 years before the present, when the population's genetic diversity began to decline dramatically. The timing of this decline correlates with environmental changes associated with the onset of the last glacial cycle, whereas archaeological evidence does not support the presence of large populations of humans in Eastern Beringia until more than 15,000 years later.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Shapiro, Beth -- Drummond, Alexei J -- Rambaut, Andrew -- Wilson, Michael C -- Matheus, Paul E -- Sher, Andrei V -- Pybus, Oliver G -- Gilbert, M Thomas P -- Barnes, Ian -- Binladen, Jonas -- Willerslev, Eske -- Hansen, Anders J -- Baryshnikov, Gennady F -- Burns, James A -- Davydov, Sergei -- Driver, Jonathan C -- Froese, Duane G -- Harington, C Richard -- Keddie, Grant -- Kosintsev, Pavel -- Kunz, Michael L -- Martin, Larry D -- Stephenson, Robert O -- Storer, John -- Tedford, Richard -- Zimov, Sergei -- Cooper, Alan -- New York, N.Y. -- Science. 2004 Nov 26;306(5701):1561-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Henry Wellcome Ancient Biomolecules Centre, Oxford University, South Parks Road, Oxford OX13PS, UK.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15567864" target="_blank"〉PubMed〈/a〉
    Keywords: Alaska ; Animals ; Bayes Theorem ; *Bison/classification/genetics ; Canada ; China ; *Climate ; DNA, Mitochondrial/genetics ; Environment ; *Fossils ; Genetic Variation ; Genetics, Population ; Human Activities ; Humans ; North America ; Phylogeny ; Population Dynamics ; Sequence Analysis, DNA ; Time
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Intracellular acidosis enhances the excitability of working muscle (2004)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2004-08-25
    Description: Intracellular acidification of skeletal muscles is commonly thought to contribute to muscle fatigue. However, intracellular acidosis also acts to preserve muscle excitability when muscles become depolarized, which occurs with working muscles. Here, we show that this process may be mediated by decreased chloride permeability, which enables action potentials to still be propagated along the internal network of tubules in a muscle fiber (the T system) despite muscle depolarization. These results implicate chloride ion channels in muscle function and emphasize that intracellular acidosis of muscle has protective effects during muscle fatigue.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Pedersen, Thomas H -- Nielsen, Ole B -- Lamb, Graham D -- Stephenson, D George -- New York, N.Y. -- Science. 2004 Aug 20;305(5687):1144-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Physiology, University of Aarhus, DK-8000, Denmark.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15326352" target="_blank"〉PubMed〈/a〉
    Keywords: Action Potentials ; Animals ; Calcium/metabolism ; Chloride Channels/*metabolism ; Chlorides/metabolism ; Electric Stimulation ; Hydrogen-Ion Concentration ; In Vitro Techniques ; Lactic Acid/metabolism ; Membrane Potentials ; Muscle Contraction ; *Muscle Fatigue ; Muscle Fibers, Skeletal/metabolism/*physiology ; Muscle, Skeletal/metabolism/*physiology ; Permeability ; Potassium/metabolism ; Rats ; Sarcoplasmic Reticulum/metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 5
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    Peptides enhance magnesium signature in calcite: insights into origins of vital effects (2008)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2008-11-01
    Description: Studies relating the magnesium (Mg) content of calcified skeletons to temperature often report unexplained deviations from the signature expected for inorganically grown calcite. These "vital effects" are believed to have biological origins, but mechanistic bases for measured offsets remain unclear. We show that a simple hydrophilic peptide, with the same carboxyl-rich character as that of macromolecules isolated from sites of calcification, increases calcite Mg content by up to 3 mole percent. Comparisons to previous studies correlating Mg content of carbonate minerals with temperature show that the Mg enhancement due to peptides results in offsets equivalent to 7 degrees to 14 degrees C. The insights also provide a physical basis for anecdotal evidence that organic chemistry modulates the mineralization of inorganic carbonates and suggest an approach to tuning impurity levels in controlled materials synthesis.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stephenson, A E -- DeYoreo, J J -- Wu, L -- Wu, K J -- Hoyer, J -- Dove, P M -- New York, N.Y. -- Science. 2008 Oct 31;322(5902):724-7. doi: 10.1126/science.1159417.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geosciences, Virginia Tech, Blacksburg, VA 24061, USA. aestephe@vt.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18974348" target="_blank"〉PubMed〈/a〉
    Keywords: Calcification, Physiologic ; Calcium/analysis ; Calcium Carbonate/*chemistry ; Crystallization ; Geologic Sediments/chemistry ; Magnesium/*analysis ; Microscopy, Atomic Force ; Peptides/*chemistry ; Temperature ; Thermodynamics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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