Neither xylem collapse, cavitation, or changing leaf conductance drive stomatal closure in wheat
Déborah Corso, Sylvain Delzon, Laurent J. Lamarque, Hervé Cochard, José Manuel Torres Ruiz, Andrew King, Timothy J. Brodribb
Abstract
Abstract Identifying the drivers of stomatal closure and leaf damage during stress in grasses is a critical prerequisite for understanding crop resilience. Here, we investigated whether changes in stomatal conductance ( g s ) during dehydration were associated with changes in leaf hydraulic conductance ( K leaf ), xylem cavitation, xylem collapse, and leaf cell turgor in wheat ( Triticum aestivum ). During soil dehydration, the decline of g s was concomitant with declining K leaf under mild water stress. This early decline of leaf hydraulic conductance was not driven by cavitation, as the first cavitation events in leaf and stem were detected well after K leaf had declined. Xylem vessel deformation could only account for <5% of the observed decline in leaf hydraulic conductance during dehydration. Thus, we concluded that changes in the hydraulic conductance of tissues outside the xylem were responsible for the majority of K leaf decline during leaf dehydration in wheat. However, the contribution of leaf resistance to whole plant resistance was less than other tissues (<35% of whole plant resistance), and this proportion remained constant as plants dehydrated, indicating that K leaf decline during water stress was not a major driver of stomatal closure.