Effects of Water Stress on Sorbitol Content in Leaves and Roots, Anatomical Changes in Cell Nuclei, and Starch Accumulation in Leaves of Young Peach Trees

Abstract

The effects of water stress on sorbitol content in the leaves and roots of young 'Ohatsumomo' peach seedlings, as well as anatomical changes to nuclei and starch accumulation in the cells of the leaves were investigated. The degree of water stress was graded into four levels: unstressed plots (control), weakly stressed plots (w-plots), mildly stressed plots (m-plots) and severely stressed plots (s-plots). The degree of water stress was judged by the extent of the leaves wilted and was estimated by the water saturation deficiency (WSD) of the leaves. Water stress increased sorbitol content in leaves but not in roots. Although the WSD of the leaves increased significantly with increasing water stress, drought treatment caused only slight differences in sorbitol content in the leaves. One day after watering, the sorbitol content of the treatments decreased to the levels similar to those of unstressed trees. Few leaves of w-plots and m-plots abscised after watering; but leaves of s-plots abscised severely, and some trees died. Starch accumulation in the mesophyll parenchyma decreased with increasing water stress. After recovery from water stress, starch grains accumulated again in the leaves. Nuclear degradation in the mesophyll parenchyma was observed only in s-plots but not in the w- and m-plots.