Gibberellin A3 induced flowering intensification in Humulus lupulus L.: Synchronizing vegetative phase change and photoperiod induction

Abstract

Exogenous gibberellic acid (GA3) treatments applied to shoot apical meristematic tissue prior to or simultaneously with the start of short day photoinduction stimulated flower set of Humulus lupulus L. (hop) cultivar ‘Centennial’. Applications during the vegetative phase change resulted in the largest flower set promotion. GA3 dosage and time of application relative to the start of the photoinductive period also influenced flower set stimulation. GA3 applied post photoperiod induction resulted in less flowering promotion and more cell expansion. The results show, for the first time, a GA3 flower stimulation relationship that encompasses tissue and bine development, rate-of-application, vegetative phase change, and photoinduction timing. This study provides a protocol for efficient application of GA3 to enhance hop flower set, which may be relevant for future studies that reexamine exogenous GA3 flowering control in commercial hop production.