Flower Bud Dormancy inCoffea ArabicaL. I. Studies of Gibberellin in Flower Buds and Xylem Sap and of Abscisic Acid in Flower Buds in Relation to Dormancy Release

Abstract

SummaryChanges were studied in gibberellin and abscisic acid in coffee flower buds and gibberellin in xylem sap when bud dormancy was released by rainfall or irrigation. Gibberellin levels in the buds increased rapidly, while those in the xylem sap remained unchanged. Bud gibberellin stopped rising when rapid expansion began and then decreased as this proceeded. The absolute amount of abscisic acid in buds remained steady prior to increasing just before anthesis. On a fresh weight basis levels declined during rapid water uptake but recovered as anthesis approached. The resumption of active growth leading to blossoming may be regulated by the liberation of free gibberellin from a bound form in the buds, but a second, xylem-transported, stimulus could also be involved.A column chromatographic technique using silicic acid for the separation of gibberellin and abscisic acid is described.