Effect of aqueous application of GA3 on flowering of mango trees: why in certain instances is flowering prevented, and in others flowering is only delayed?
Oosthuyse S. A.
Author Affiliation: Merensky Technological Services, PO Box 14, Duivelskloof 0835, South Africa.
Yearbook - South African Mango Growers' Association 15 : 21-25
Abstract : Sensation mango trees were sprayed with GA3 at 200 p.p.m. in mid-June, when the apical buds were at varying stages of floral differentiation. Budbreak was either inhibited, or 'pure' inflorescences, leafy inflorescences, inflorescence/shoot-like structures (intermediary inflorescences), or shoots developed shortly after treatment. When different GA3 concentrations (25-200 p.p.m.) were applied, the extent repression of inflorescence development was positively related to GA3 concentration. When Sensation, Tommy Atkins, Heidi, Kent, Zill and Keitt mango trees sprayed with GA3 (100 p.p.m.) at 14-day intervals from 20 Apr. until 24 Aug. (one spray per tree), the number of inflorescences and intermediary inflorescences developing per tree showed considerable variation in relation to both application date and cultivar. However, application in late July or early Aug., which was accompanied by pruning to remove the apical buds and any inflorescences present at the time of spraying, resulted in the prevention of further flowering. These results suggest that GA3 inhibits budbreak of dormant buds and represses continued inflorescence differentiation when applied to differentiating floral buds. Furthermore, it would appear that GA3 is generally effective in preventing flowering if it delays budbreak to a period when environmental conditions are less inductive for flowering, otherwise GA3 may act to delay flowering.