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Abstract Detail


Ecophysiology

Cornwell, W K [1], Santiago, L S [2], Wright, Ian J. [3], Barbour, M M [4], Buchmann, N [5], Cernusak, L A [6], Dawson, Todd [7], Ellsworth, D S [8], Farquhar, G D [9], Griffiths, H [10], Keitel, C [9], Knohl, A [5], Martinelli, L A [11], Reich, P B [12], Williams, David [13], Westoby, Mark [14].

Regulation of carbon isotope discrimination during C3 photosynthesis: Results from a global database.

Within plants utilizing the C3 photosynthetic pathway, discrimination against the stable isotope carbon-13 records information about the intercellular CO2 concentration during photosynthesis, thereby providing insights into how plants interact with their environment. We present results from a global database of leaf carbon isotopes containing nearly 4000 species-site combinations and representing angiosperms, gymnosperms, ferns and bryophytes. Our analyses focus on relationships between climate and carbon isotope discrimination during photosynthesis, as well as regulation by common indices of leaf physiological function such as maximum photosynthetic rate, stomatal conductance, specific leaf area, and leaf nitrogen concentration. We determined that over 50% of global variation in leaf carbon isotope ratios within C3 plants is explained by climate variables. Discrimination (indicating higher CO2 concentration at the site of carboxylation) is higher at low elevation, high rainfall, warmer temperature, low radiation, and low vapor pressure deficit environments. Our analyses also demonstrate a negative effect of the ratio of photosynthetic rate to stomatal conductance, as well as a negative effect of leaf nitrogen concentration on discrimination, consistent with current models that account for the balance between the demand for CO2 at the site of carboxylation and the diffusive supply through stomata. Greater discrimination in leaves with high specific leaf area is consistent with the expected role of internal conductance across the global dataset. Physiological mechanisms of cross-species variation in leaf carbon isotopic composition will be further discussed.


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1 - Biodiversity Centre, UBC
2 - University of California, Riverside
3 - Macquarie University, Department of Biological Sciences, Sydney, NSW, 2109, Australia
4 - Landcare Research
5 - ETH Zurich
6 - Charles Darwin University
7 - University of California, Berkeley, Department of Integrative Biology, 3060 Valley Life Sciences Bldg #3140, Berkeley, California, 94720, USA
8 - University of Western Sydney
9 - Australian National University
10 - University of Cambridge
11 - Universidade de Sao Paulo
12 - University of Minnesota
13 - University of Wyoming, Renewable Resources and Botany, Dept 3354, 1000 E University Ave., Laramie, Wyoming, 82071, USA
14 - Macquarie University, Department of Biological Sciences, North Ryde, New South Wales, 2109, Australia

Keywords:
carbon isotope discrimination
Photosynthesis
global inventory
climate
leaf traits.

Presentation Type: Oral Paper:Papers for Topics
Session: 22
Location: 207/SUB
Date: Monday, July 28th, 2008
Time: 2:00 PM
Number: 22003
Abstract ID:849


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