An abscisic acid-related reduced transpiration promotes gradual embolism repair when grapevines are rehydrated after drought

摘要

Proposed mechanisms of embolism recovery are controversial for plants that are transpiring while undergoing cycles of dehydration and rehydration. Here, water stress was imposed on grapevines (Vitis vinifera), and the course of embolism recovery, leaf water potential (.leaf), transpiration (E) and abscisic acid (ABA) concentration followed during the rehydration process. As expected, .leaf and E decreased upon water stress, whereas xylem embolism and leaf ABA concentration increased. Upon rehydration, .leaf recovered in 5 h, whereas E fully recovered only after an additional 48 h. The ABA content of recovering leaves was higher than in droughted controls, both on the day of rewatering and the day after, suggesting that ABA accumulated in roots during drought was delivered to the rehydrated leaves. In recovering plants, xylem embolism in petioles, shoots, and roots decreased during the 24 h following rehydration. A model is proposed to describe plant recovery after rehydration based on three main points: embolism repair occurs progressively in shoots and further in roots and in petioles, following an almost full recovery of .leaf; hydraulic conductance recovers during diurnal transpiring hours, when formation and repair of embolisms occurs in all plant organs; an ABA residual signal in rehydrated leaves hinders stomatal opening even when water relations have recovered, suggesting that an ABA-induced transpiration control promotes gradual embolism repair in rehydrated grapevines.