EFFECT OF GA4-CHANGE IN UNICONAZOLE-TREATED HIBISCUS(7 ON GROWTH AND CELLULAR)

Hibiscus rosa-sinensis 'Jane Cowl' in 1.5-1 pots were given a soil dre nch of 0.2 mg uniconazole, pruned 2 weeks later, and treated with a fo liar application of GA4+7 at 0, 25 (once or four times every 2 weeks), 50 (once or twice every 4 weeks), or 100 mg L-1. One application of G A4+7 at 100 mg L-1, two applications at 50 mg L-1, and four applicatio ns at 25 mg L-1 were more active in partially restoring stem elongatio n and caused nearly normal leaf production than other GA treatments, b ut promoted the abscission of the lower leaves. The size of the indivi dual leaves, but not stem diameter, increased following GA4+7 applicat ion. Multiple applications of GA4+7 stimulated flowering of the retard ed plants. Uniconazole resulted in short pedicels bearing short cells with increased diameter, as well as larger pith, vascular, and cortica l tissues than the untreated control. Four applications of 25 mg L-1 G A4+7 to uniconazole-treated plants resulted in long pedicels, having l ong cells similar to the control. Results of the histological study su ggest that uniconazole either slowed cell division or caused cell divi sion to cease early.