Gibberellins in relation to flowering in Polianthes tuberosa.

Abstract

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 A1, A19, A20 and A53 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 GA1 and GA20, and a decrease in GA19 levels, coincided with the transition from the vegetative phase to the stages of early floral initiation and flower development. GA53 stayed at constant levels at the 3 different growth stages. The absence of GA1 in vegetative corms and its presence in corms at early floral initiation and flower development stages suggest that GA1 is a causal factor in inducing floral initiation in P. tuberosa. When GA1, GA3, GA4, GA20 and GA32 were applied to corms at the vegetative stage (plants about 5 cm in height), floral initiation was promoted by all of the GAs used, GA32 being the most active. In contrast with the other GAs, GA32 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.