The use of ultrasonic detectors for water stress determination in fruit trees

Abstract

Introduction In drought, the hydraulic conductance in tree stems can be reduced by embolisms that occur within xylem vessels and tra-cheids. There is good circumstantial evidence that these cavitation events can be detected acoustically, either at low frequency , i.e., 0.2-2 kHz (Milburn and John-son, 1966) or high frequency, i.e., 0.1-1.0 MHz (Tyree and Dixon, 1983) It is important to know at what stage cavitations occur and whether there are inherent differences between varieties or species. As a tool to investigate cavitation events, we have used ultrasound detectors, since they are able to operate in a noisy environment or in field conditions without background interference.