EFFECT OF GROWTH-REGULATING SUBSTANCES ON GROWTH OF HIBISCUS TREATED WITH UNICONAZOLE

Abstract

Hibiscus rosa-sinensis `Jane Cowl' were pruned several weeks after receiving 0.1 mg/pot uniconazole soil drenches to retard the growth. Plants then received foliar sprays of GA3 (50 ppm), KIBA (200 ppm), or PBA (200 ppm) immediately after pruning or when the lateral shoots had three leaves. Application of the above growth regulators immediately after pruning had no effect on plant growth. When treatments were delayed until the three-leaf stage, GA3 completely restored leaf production rate and partially restored shoot elongation and pedicel length. GA3 also increased leaf area, and the leaf specific weight was similar to leaves on plants not receiving uniconazole. GA3 increased flower production 175% and 65% more than plants treated with uniconazole and the untreated plants, respectively. KIBA and PBA had no effect on altering the growth of uniconazole-treated plants. Foliar application of a combination of GA3, KIBA and PBA at the three-leaf stage had an effect similar to that of GA3 alone. However, the effect of GA3 on growth appeared to be transient and repeated application may be required to maintain the restored growth of uniconazole-treated plants.