Effects of Thinning, Physiological Stress and Gibberellic Acid on Hibiscus Flower Growth and Development

Background and Objectives: Hibiscus plant (Rosa sinensis) is an important in the field of ornamental plant. Its beautiful blooms make its perfect in the environmental beautification. The study was undertaken to evaluate the effects of thinning, phloem cut stress (represented by bark ringing) and hormone application (Gibberellic acid, GA₃) on the flowers development and the longevity. Materials and Methods: Excess leaves were discarded from the branches in the range of 20 cm. A 3 cm length of bark was removed from the trunk leaving 4 mm width connecting bark band. The GA₃ of 20 mg L^–1 concentration was sprayed to the branches twice a week. Number of buds and leaves, leaf size, flower size, petal diameter, flower weight, chlorophyll a, b and total carotenoid contents were examined. Results: The result showed that GA₃ application was most effective in delaying senescence followed by phloemic stress and thinning. The GA₃ application to the flowers induced highest number of buds and leaves, biggest size of flowers, leaves and also showed a delay in flower wilting and discoloration. Chlorophyll b and carotenoid contents were also highest in flowers treated with GA₃. However, flowers with no treatment (control) exhibited highest content of chlorophyll a. Conclusion: These results indicate that hormone application (GA₃) was the best treatment to extend the longevity of Hibiscus rosa-sinensis. The use of this hormone would be of a great help in flower industry.