Endogenous gibberellins (GAs) in corms of Polianthes tuberosa L. (cv. Doubl
e) 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 vegetat
ive, early floral initiation and flower development stages. The identificat
ion of 13-hydroxylated GAs indicates the presence of the early 13-hydroxyla
tion pathway in P. tuberosa corms, An increase in GA(1) and GA(20), and a d
ecrease 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 ini
tiation 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 e
ffect on stem elongation. Therefore, it is suggested that hydroxylated C-19
GAs play an important role in flower induction in P. tuberosa.