EFFECT OF BRASSINOLIDE ON LEVELS OF INDOLEACETIC-ACID AND ABSCISIC-ACID IN SQUASH HYPOCOTYLS - POSSIBLE APPLICATION FOR PREVENTING FRUIT ABORTION

Brassinolide stimulated an increase in fresh weight of segments of hypocotyls of etiolated squash (Cucurbita maxima Duch.). Brassinolide-treated segments contained a slightly higher level of IAA than water-treated segments and also showed a tendency towards decreased level of ABA. Flowers of 'Morita' navel oranges were treated with brassinolide solution at anthesis. Fruit set of trees treated with 0.1 and 0.01 ppm brassinolide increased by ca. 5 and 2.5 times respectively, when surveyed 50 days after treatment. At harvest there were no differences in quality between treated and untreated fruits. Since brassinolide-treated squash segments only showed slight changes in hormone content, brassinolide may have a direct action on stimulating fruit set without marked changes in the levels of other endogenous phytohormones.