Gibberellins in relation to flowering in Polianthes tuberosa

Endogenous gibberellins (GAs) in corms of Polianthes tuberosa L. (cv. Double) were isolated and identified by high performance liquid chromatography, bioassay and combined capillary gas chromatography-mass spectrometry (GC-MS). Gibberellins A 1 , A 19 , A 20 and A 53 were quantified at the vegetative, early floral initiation and flower development stages. The identification of 13-hydroxylated GAs indicates the presence of the early 13-hydroxylation pathway in P. tuberosa corms. An increase in GA 1 and GA 20 , and a decrease in GA 19 levels, coincided with the transition from the vegetative phase to the stages of early floral initiation and flower development. GA 53 stayed at constant levels at the 3 different growth stages. The absence of GA 1 in vegetative corms and its presence in corms at early floral initiation and flower development stages suggest that GA 1 is a causal factor in inducing floral initiation in P. tuberosa. When GA 1 , GA 3 , GA 4 , GA 20 and GA 32 were applied to corms at the vegetative stage (plants about 5 cm in height), floral initiation was promoted by all of the GAs used, GA 32 being the most active. In contrast with the other GAs, GA 32 had no effect on stem elongation. Therefore, it is suggested that hydroxylated C-19 GAs play an important role in flower induction in P. tuberosa.