Time and method of floral initiation and effect of paclobutrazol on flower and fruit development in Shorea stenoptera (Dipterocarpaceae)

Small Shorea stenoptera Burck. (Dipterocarpaceae) trees of reproductive age growing in an arboretum in west Java were studied to determine the pattern of vegetative shoot development, the time and method of floral initiation and the effect of paclobutrazol on floral enhancement. Vegetative buds were enclosed by two stipules between which was a leaf primordium, a small axillary vegetative bud and another pair of stipules. This sequence was reiterated five to seven times before the vegetative apex was visible. At the time of floral initiation, axillary buds developed into floral spikes and compound inflorescences formed at the end of drooping branches. A compound inflorescence might bear many floral spikes and each floral spike bore many flowers. The compound inflorescence was a modification of the reiterative developmental pattern observed in vegetative shoots. The time of floral initiation began in late June or early July and continued until about November. Floral enhancement using paclobutrazol as a soil drench was attempted in mid-July, but this was later found to be after the onset of floral initiation, and the treatment failed to enhance flowering; however, it appeared to enhance the rate of floral and fruit development. The similarity in vegetative bud development among dipterocarp genera suggests that the time of floral initiation may be easily determined in many species based on simple dissection techniques.