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Effect of water availability on leaf water isotopic enrichment in beech seedlings shows limitations of current fractionation models
Author(s) -
FERRIO JUAN PEDRO,
CUNTZ MATTHIAS,
OFFERMANN CHRISTINE,
SIEGWOLF ROLF,
SAURER MATTHIAS,
GESSLER ARTHUR
Publication year - 2009
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.2009.01996.x
Subject(s) - beech , transpiration , delta , stomatal conductance , environmental science , current (fluid) , evaporation , botany , chemistry , environmental chemistry , photosynthesis , biology , geology , oceanography , physics , thermodynamics , engineering , aerospace engineering
Current models of leaf water enrichment predict that the differences between isotopic enrichment of water at the site of evaporation (Δ e ) and mean lamina leaf water enrichment (Δ L ) depend on transpiration rates ( E ), modulated by the scaled effective length ( L ) of water isotope movement in the leaf. However, variations in leaf parameters in response to changing environmental conditions might cause changes in the water path and thus L . We measured the diel course of Δ L for 18 O and 2 H in beech seedlings under well‐watered and water‐limited conditions. We applied evaporative enrichment models of increasing complexity to predict Δ e and Δ L , and estimated L from model fits. Water‐limited plants showed moderate drought stress, with lower stomatal conductance, E and stem water potential than the control. Despite having double E , the divergence between Δ e and Δ L was lower in well‐watered than in water‐limited plants, and thus, L should have changed to counteract differences in E . Indeed, L was about threefold higher in water‐limited plants, regardless of the models used. We conclude that L changes with plant water status far beyond the variations explained by water content and other measured variables, thus limiting the use of current evaporative models under changing environmental conditions.