Seasonal Changes of Free and Hydrolyzable Abscisic Acid in Vegetative Apple Buds1

Abstract

Levels of free and hydrolyzable abscisic acid (ABA, H-ABA) in vegetative apple (Malus domestica Borkh.) buds were measured by electron capture gas chromatography. ABA level was high during midsummer both before and after entry into dormancy, increased to a maximum just prior to leaf fall, and decreased to a minimum just prior to bloom. H-ABA level was low during midsummer, increased gradually during fall and winter, reached a maximum during the early stages of bud development, and then decreased very rapidly just prior to full bloom.