Endogenous Growth Substances in Relation to Shoot Growth and Flower Bud Development of Mango

Abstract

Changes in gibberellin and cytokinin activities were investigated at the stages of leaf differentiation, mature green leaves, early flower bud formation (7 days after formation), and full bloom of 3-year-old mangos (Mangifera indica L.) in pot culture. Also, diffusible IAA and ABA in the diffusate of shoot tips were examined at the different developing stages. High gibberellin and diffusable IAA activity was found in the xylem sap at leaf differentiation. Diffusible IAA decreased to a low level in shoot tip diffusates, and ABA increased dramatically during early flower bud formation. At the same time, total cytokinin-like activity increased in the xylem sap, reaching a maximum level at full bloom. Chemical names used: 1H-indole-3-acetic acid (IAA); [S-(Z,E)]-5-(l-hydroxy-2,6,6-trimethyl-4-oxo-2-cyclohexen-1-yl)-3-methyl-2,4-pentadienoic acid [abscisic acid (ABA)].