The oxygen isotope enrichment of bulk leaf water (Db) was measured in cotton (Gossypium hirsutum) leaves to test the Craig- Gordon and Farquhar-Gan models under different environmental conditions. Db increased with increasing leaf-to-air vapor pressure difference (VPd) as an overall result of the responses to the ratio of ambient to intercellular vapor pressures (ea/ei) and to stomatal conductance (gs). The oxygen isotope enrichment of lamina water relative to source water ðD1Þ; which increased with increasing VPd, was estimated by mass balance between less enriched water in primary veins and enriched water in the leaf. The Craig-Gordon model overestimated Db (and D1Þ; as expected. Such discrepancies increased with increase in transpiration rate (E), supporting the Farquhar-Gan model, which gave reasonable predictions of Db and D1 with an L of 7.9 mm, much less than the total radial effective length Lr of 43 mm. The fitted values of L for D1 of individual leaves showed little dependence on VPd and temperature, supporting the assumption that the Farquhar-Gan formulation is relevant and useful in describing leaf water isotopic enrichment.

Environmental Effects on Oxygen Isotope Enrichment of Leaf Water in Cotton Leaves

RIPULLONE, Francesco
Writing – Original Draft Preparation
;
BORGHETTI, Marco
Supervision
;
2008

Abstract

The oxygen isotope enrichment of bulk leaf water (Db) was measured in cotton (Gossypium hirsutum) leaves to test the Craig- Gordon and Farquhar-Gan models under different environmental conditions. Db increased with increasing leaf-to-air vapor pressure difference (VPd) as an overall result of the responses to the ratio of ambient to intercellular vapor pressures (ea/ei) and to stomatal conductance (gs). The oxygen isotope enrichment of lamina water relative to source water ðD1Þ; which increased with increasing VPd, was estimated by mass balance between less enriched water in primary veins and enriched water in the leaf. The Craig-Gordon model overestimated Db (and D1Þ; as expected. Such discrepancies increased with increase in transpiration rate (E), supporting the Farquhar-Gan model, which gave reasonable predictions of Db and D1 with an L of 7.9 mm, much less than the total radial effective length Lr of 43 mm. The fitted values of L for D1 of individual leaves showed little dependence on VPd and temperature, supporting the assumption that the Farquhar-Gan formulation is relevant and useful in describing leaf water isotopic enrichment.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11563/966
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