The Péclet effect on leaf water enrichment correlates with leaf hydraulic conductance and mesophyll conductance for CO 2

Leaf water gets isotopically enriched through transpiration, and diffusion of enriched water through the leaf depends on transpiration flow and the effective path length ( L ). The aim of this work was to relate L with physiological variables likely to respond to similar processes. We studied the response to drought and vein severing of leaf lamina hydraulic conductance ( K lamina ), mesophyll conductance for CO 2 ( g m ) and leaf water isotope enrichment in Vitis vinifera L cv. Grenache. We hypothesized that restrictions in water pathways would reduce K lamina and increase L . As a secondary hypothesis, we proposed that, given the common pathways for water and CO 2 involved, a similar response should be found in g m . Our results showed that L was strongly related to mesophyll variables, such as K lamina or g m across experimental drought and vein‐cutting treatments, showing stronger relationships than with variables included as input parameters for the models, such as transpiration. Our findings were further supported by a literature survey showing a close link between L and leaf hydraulic conductance ( K leaf  = 31.5 ×  L −0.43 , r 2  = 0.60, n  = 24). The strong correlation found between L, K lamina and g m supports the idea that water and CO 2 share an important part of their diffusion pathways through the mesophyll.