Gibberellic acid and cytokinin affect Phalaenopsis flower morphology at high temperature

Gibberellin A(3) (GA(3): 1, 3, or 5 mu g/shoot), N-6-benzyladenine (BA: 1, 3, or 5 mu g/shoot), or both were applied to the flowering shoots of a white hybrid Phalaenopsis orchid (Leda) when they were 2 to 3 cm (stage 1, no flower primordia) long at high temperature (30 degrees C day/25 degrees C night). When flowering shoots were treated with GA(3) alone, deformed flowers were more frequent with increasing GA(3) concentrations. The occurrence of GA(3)-induced deformed flowers was prevented by BA at the same dose as GA(3) when applied 4 days after GA(3) treatment. BA (1, 3, or 5 mu g/shoot) was also applied 4 days before (time 1) or 4 days after (time 2) GA(3) (1 mu g/shoot) treatment for regulating plant characteristics. The application of EA at 1 or 5 mu g/shoot to stage 1 flowering shoots at time 2 resulted in short internodes between florets, whereas BA application at time 1 had no effect, Simultaneously, BA at 1 or 5 mu g/shoot applied at time 1 or time 2 to stage 2 (5 to 6 cm long, two- to three-flower primordia) flowering shoots also shortened internode length between florets as compared to GA(3) alone. When a stage 1 flowering shoot was given BA (3 or 5, but not 1 mu g/shoot) and then treated with GA(3) 4 days later, flower count was slightly reduced as compared to treating with GA(3) alone. However, a high dose of BA applied at time 1 or time 2 on stage 2 flowering shoots had no effect on flower count. Chemical names used: N-(phenylmethyl)-1H-purine-6-amine [benzyladenine (BA)], gibberellic acid (GA(3)).