Plant water status of apple trees and its measurement in the field. 7. Week-to-week variations in the early morning plant water status of three varieties

Abstract

Leaf water potential, fruit water potential and leaf infiltration scores were used as indices of the plant water status of three apple varieties, during one growing season. The highest and lowest leaf water potentials recorded, during the early morning period, were respectively for Delicious .9 atm and -20 atm, Jonathan -3.5 atm and -19 atm, and Granny Smith -4 atm and -13 atm. Mean fruit water potential was similar for Granny Smith and Delicious, but considerably lower for Jonathan. Leaf infiltration scores and leaf water potential maintained a close relationship, while leaf and fruit water potentials showed considerable divergence. These data serve to show the magnitude of plant water stress which apple trees have to contend with in an almost normal growing season in Queensland.