SIGNIFICANCE OF HORMONES ON FLOWER BUD INITIATION AND FRUIT QUALITY IN APPLE: OUR EXPERTISE

A contribution on the possible involvement of plant hormones in the process of flower formation and fruit quality in apple is presented. When zeatin was injected to spurs via a cut petiole, an increase on return bloom was observed. Radioactivity of zeatin accumulated mainly in the bourse bud when applied through the same application method. At the time of flower initiation, a high level of cytokinins was found in immature seeds; whereas low activity of these hormones was detected in xylem sap. Endogenous gibberellins were less than cytokinins in seeds, whilst in xylem sap these hormones were slightly higher. Prohexadione-Ca (P-Ca) inhibited the synthesis of gibberellins A₁, A₄ and A₇ in shoot tips. The total antioxidant content in ripening fruits was increased by P-Ca. This growth retardant also promoted an increase in vitamin C.