Directional change in leaf dry matter δ 13C during leaf development is widespread in C3 plants.

Autor: Vogado NO; Centre for Tropical Environmental and Sustainability Science, College of Science and Engineering, James Cook University, Cairns, Australia., Winter K; Smithsonian Tropical Research Institute, Balboa, Ancon, Republic of Panama., Ubierna N; Research School of Biology, The Australian National University, Canberra, Australia., Farquhar GD; Research School of Biology, The Australian National University, Canberra, Australia., Cernusak LA; Centre for Tropical Environmental and Sustainability Science, College of Science and Engineering, James Cook University, Cairns, Australia.
Jazyk: angličtina
Zdroj: Annals of botany [Ann Bot] 2020 Oct 30; Vol. 126 (6), pp. 981-990.
DOI: 10.1093/aob/mcaa114
Abstrakt: Background and Aims: The stable carbon isotope ratio of leaf dry matter (δ 13Cp) is generally a reliable recorder of intrinsic water-use efficiency in C3 plants. Here, we investigated a previously reported pattern of developmental change in leaf δ 13Cp during leaf expansion, whereby emerging leaves are initially 13C-enriched compared to mature leaves on the same plant, with their δ 13Cp decreasing during leaf expansion until they eventually take on the δ 13Cp of other mature leaves.
Methods: We compiled data to test whether the difference between mature and young leaf δ 13Cp differs between temperate and tropical species, or between deciduous and evergreen species. We also tested whether the developmental change in δ 13Cp is indicative of a concomitant change in intrinsic water-use efficiency. To gain further insight, we made online measurements of 13C discrimination (∆ 13C) in young and mature leaves.
Key Results: We found that the δ 13Cp difference between mature and young leaves was significantly larger for deciduous than for evergreen species (-2.1 ‰ vs. -1.4 ‰, respectively). Counter to expectation based on the change in δ 13Cp, intrinsic water-use efficiency did not decrease between young and mature leaves; rather, it did the opposite. The ratio of intercellular to ambient CO2 concentrations (ci/ca) was significantly higher in young than in mature leaves (0.86 vs. 0.72, respectively), corresponding to lower intrinsic water-use efficiency. Accordingly, instantaneous ∆ 13C was also higher in young than in mature leaves. Elevated ci/ca and ∆ 13C in young leaves resulted from a combination of low photosynthetic capacity and high day respiration rates.
Conclusion: The decline in leaf δ 13Cp during leaf expansion appears to reflect the addition of the expanding leaf's own 13C-depleted photosynthetic carbon to that imported from outside the leaf as the leaf develops. This mixing of carbon sources results in an unusual case of isotopic deception: less negative δ 13Cp in young leaves belies their low intrinsic water-use efficiency.
(© The Author(s) 2020. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)
Databáze: MEDLINE
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