Effect of gibberellins A3, A 4+7 and A 13 and of (-)-kaurene on flowering and extension growth of Impatiens balsamina under different photoperiods.

Gibberellins A3, A4+7 and A13 and (-)-kaurene delay floral-bud initiation and flowering and decrease the number of floral-buds and flowers in Impatiens balsamina under 4-hr photoperiods. They do not have any marked effect under 8-hr photoperiods. Under 16- and 24-hr photoperiods they hasten floral-bud initiation and flowering and increase the number of flowers, the effect being greater under 16- than under 24-hr days and the order of effectiveness being GA4+7>GA3>GA13>(-)-kaurene.While GA3 and GA4+7 promote extension growth, the effect being greater with the former, GA13 and (-)-kaurene do not promote it under any photoperiod. The magnitude of stem elongation in different treatments prior to floral-bud initiation increases from 4- to 8-hr photoperiods but decreases under 16- and 24-hr periods, the effect being more under 24-hr although both 16-and 24-hr photoperiods are noninductive for flowering.