Hydraulic conductivity and vulnerability to cavitation in relation with water stress in grapevine (cv. Chasselas)

Abstract

The petiole hydraulic conductance (K_petioles) and the vulnerability to cavitation (PLC, percentage loss of hydraulic conductivity) in leaf petioles and stems were monitored on field-grown vines (Vitis vinifera L. cv. Chasselas). The petioles were highly vulnerable to cavitation with a 50% loss of hydraulic conductivity when stem water potential (ѱ_stem) reached -1.1 MPa approximately. The stems were more resistant to the embolism events with 50% of PLC at -1.4 MPa of ѱ_stem. Our results showed that daily and seasonal variations of K_petiole strongly correlated with the level of water stress. The K_petiole followed a daily cycle, decreasing during the day when the water stress and the climatic demand (air vapour pressure deficit, VPD) were high, and then rising again from early evening to attain the K_petiole levels of the previous morning. In the water-stressed vines, PLC increased in the afternoon when the climatic demand was high and then decreased at night. The petiole cavitation seems to play an important role as “hydraulic fuse” limiting the propagation of embolism and preserving the hydraulic integrity of the other organs (shoots, clusters).