Non-steady-state, non-uniform transpiration rate and leaf anatomy effects on the progressive stable isotope enrichment of leaf water along monocot leaves

Abstract : This study focuses on the spatial patterns of transpiration-driven water isotope enrichment (Delta(lw)) along monocot leaves. It has been suggested that these spatial patterns are the result of competing effects of advection and (back-)diffusion of water isotopes along leaf veins and in the mesophyll, but also reflect leaf geometry (e.g. leaf length, interveinal distance) and non-uniform gas-exchange parameters. We therefore developed a two-dimensional model of isotopic leaf water enrichment that incorporates new features, compared with previous models, such as radial diffusion in the xylem, longitudinal diffusion in the mesophyll, non-uniform gas-exchange parameters and non-steady-state effects. The model reproduces well all published measurements of Delta(lw) along monocot leaf blades, except at the leaf tip and given the uncertainties on measurements and model parameters. We show that the longitudinal diffusion in the mesophyll cannot explain the observed reduction in the isotope gradient at the leaf tip. Our results also suggest that the observed differences in Delta(lw) between C-3 and C-4 plants reflect more differences in mesophyll tortuosity rather than in leaf length or interveinal distance. Mesophyll tortuosity is by far the most sensitive parameter and different values are required for different experiments on the same plant species. Finally, using new measurements of non-steady-state, spatially varying leaf water enrichment we show that spatial patterns are in steady state around midday only, just as observed for bulk leaf water enrichment, but can be easily upscaled to the whole leaf level, regardless of their degree of heterogeneity along the leaf.
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Article dans une revue
Plant, Cell and Environment, Wiley, 2007, pp.367-387
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https://hal-bioemco.ccsd.cnrs.fr/bioemco-00175969
Contributeur : Philippe Peylin <>
Soumis le : lundi 1 octobre 2007 - 22:07:33
Dernière modification le : vendredi 27 juillet 2018 - 15:04:50

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  • HAL Id : bioemco-00175969, version 1

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Philippe Peylin, Jerome Ogee, Matthias Cuntz, Philippe Peylin, Thierry Bariac. Non-steady-state, non-uniform transpiration rate and leaf anatomy effects on the progressive stable isotope enrichment of leaf water along monocot leaves. Plant, Cell and Environment, Wiley, 2007, pp.367-387. 〈bioemco-00175969〉

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