Changes in polyamine pattern are involved in floral initiation and development in Polianthes tuberosa.

In the day-neutral plant Polianthes tuberosa (cv. Double) putrescine and spermine in corms at the early floral initiation stage decreased by 26 and 36%, respectively, compared with that in the vegetative stage. In contrast, a sharp increase in spermidine and cadaverine titers in corms was recorded at the early floral initiation stage. However, cadaverine in corms disappeared at the flower development stage. Polyamines in the roots were generally lower than those in the leaves and corms. In no case was the change in endogenous polyamine titers in the roots and leaves associated with floral initiation and flower development in P. tuberosa. Exogenous application of spermidine at 5, 25 or 150 microg per plant at the vegetative stage did not affect flower primordium counts. However, addition of a spermidine synthase inhibitor, cyclohexylamine, at 150 or 250 microg per plant (each dose was applied two times in total at an interval of 4 days) significantly reduced flower primordium counts, indicating that spermidine is involved in floral initiation and floral development in P. tuberosa. In P. tuberosa corms at the vegetative stage arginine decarboxylase activity rises and decreases at the early floral initiation stage. In contrast, ornithine decarboxylase activity reaches the highest level at the early floral initiation stage and declines significantly at the vegetative stage. Results indicate that an increase in spermidine and a transient increase in cadaverine titers in the corms seem characteristic of early floral initiation in P. tuberosa. It is also suggested that a significant reduction in putrescine and spermine in the corms is involved in the early floral initiation in P. tuberosa.

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 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.