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Ontogeny and leaf gas exchange mediate the carbon isotopic signature of herbaceous plants


Salmon, Y; Barnard, R L; Buchmann, N (2011). Ontogeny and leaf gas exchange mediate the carbon isotopic signature of herbaceous plants. Plant, Cell and Environment, 34(3):465-479.

Abstract

Values (Δi) predicted by a simplified photosynthetic discrimination model, based only on diffusion through air followed by carboxylation, are often used to infer ecological conditions from the 13C signature of plant organs (δ13Cp). Recent studies showed that additional isotope discrimination (d that includes mesophyll conductance, photorespiration and day respiration, and post-carboxylation discrimination) can strongly affect δ13Cp; however, little is known about its variability during plant ontogeny for different species. Effect of ontogeny on leaf gas exchange rates, Δi, observed discrimination (Δp) and d in leaf, phloem and root of seven herbaceous species at three ontogenetic stages were investigated under controlled conditions. Functional group identity and ontogeny significantly affected Δi and Δp. However, predicted Δi did not match Δp. d, strongly affected by functional group identity and ontogeny, varied by up to 14‰. d scaled tightly with stomatal conductance, suggesting complex controls including changes in mesophyll conductance. The magnitude of the changes in δ13Cp due to ontogeny was similar to that due to environmental factors reported in other studies. d and ontogeny should, therefore, be considered in ecosystem studies, integrated in ecosystem models using δ13Cp and limit the applicability of δ13Cleaf as a proxy for water-use efficiency in herbaceous plants.

Abstract

Values (Δi) predicted by a simplified photosynthetic discrimination model, based only on diffusion through air followed by carboxylation, are often used to infer ecological conditions from the 13C signature of plant organs (δ13Cp). Recent studies showed that additional isotope discrimination (d that includes mesophyll conductance, photorespiration and day respiration, and post-carboxylation discrimination) can strongly affect δ13Cp; however, little is known about its variability during plant ontogeny for different species. Effect of ontogeny on leaf gas exchange rates, Δi, observed discrimination (Δp) and d in leaf, phloem and root of seven herbaceous species at three ontogenetic stages were investigated under controlled conditions. Functional group identity and ontogeny significantly affected Δi and Δp. However, predicted Δi did not match Δp. d, strongly affected by functional group identity and ontogeny, varied by up to 14‰. d scaled tightly with stomatal conductance, suggesting complex controls including changes in mesophyll conductance. The magnitude of the changes in δ13Cp due to ontogeny was similar to that due to environmental factors reported in other studies. d and ontogeny should, therefore, be considered in ecosystem studies, integrated in ecosystem models using δ13Cp and limit the applicability of δ13Cleaf as a proxy for water-use efficiency in herbaceous plants.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Uncontrolled Keywords:δ13C, mesophyll conductance,modification of discrimination d,photosynthesis,post-carboxylation discrimination, stomatal conductance
Language:English
Date:2011
Deposited On:09 Jun 2011 11:11
Last Modified:05 Apr 2016 14:55
Publisher:Wiley-Blackwell
ISSN:0140-7791
Publisher DOI:https://doi.org/10.1111/j.1365-3040.2010.02256.x

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