HORMONAL CONTROL OF FRUIT MATURATION AND RIPENING II. CHANGES IN ABSCISIC ACID CONTENT IN APPLE FRUITS TREATED WITH GROWTH SUBSTANCES

The influence of growth substances enhancing (CEPA, NAA), or delaying (SADH) fruit ripening on ABA content during maturation of apple fruits cv. McIntosh was studied. Control fruits attached to the tree contained a low amount of ABA during the last two weeks before harvest. Fruits treated with CEPA 250 ppm alone or combined with NAA 20 ppm or with NAA 20 ppm and SADH 1000 ppm showed a considerable increase of ABA in comparison to control. The content of ABA in fruits treated by SADH 1000 ppm increased too. The possibility of the relationship of ABA and ethylene during fruit maturation and ripening is discussed.