Stomatal Closure During Leaf Dehydration, Correlation with Other Leaf Physiological Traits

Abstract

The question as to what triggers stomatal closure during leaf desiccation remains controversial. This paper examines characteristics of the vascular and photosynthetic functions of the leaf to determine which responds most similarly to stomata during desiccation. Leaf hydraulic conductance (K-leaf) was measured from the relaxation kinetics of leaf water potential (psi(l)), and a novel application of this technique allowed the response of K-leaf to psi(l) to be determined. These vulnerability curves" show that K-leaf is highly sensitive to psi(t) and that the response of stomatal conductance to psi(1) is closely f and stomatal closure, correlated with the response of K-leaf to psi(1). The turgor loss point of leaves was also correlated with K-leaf, whereas the decline in PSII quantum yield during leaf drying occurred at a lower 41, than stomatal closure. These results indicate that stomatal closure is primarily coordinated with K-leaf. However, the close proximity of psi(l) at initial stomatal closure and initial loss of K-leaf suggest that partial loss of K-leaf might occur regularly, presumably necessitating repair of embolisms.