Effect of Foliar Applied of Barassinosteroid and Gibberellic Acid on Vegetative Growth, Flowering and Chemical Constituents of Petunia hybrida plants

This study was carried out at the Nursery of Department of Floriculture, Ornamental Horticullture and Landscape Gardening, Faculty of Agriculture, Alexandria University, Alexandria, Egypt, during the growing seasons 2022 and 2023. The aim of this study was to determine the vegetative growth, flowers and characteristic components through pen test for the pen effect of barssinostroids (Brs) and gebbrellic acid (GA3) of Petunia hybrida plants. Petunia plants were sprayed with either gebbrellic acid (GA3) at three doses (zero, 100, and 200 mg/l) or barssinostroids (Brs) at four concentrations (zero, 1, 2, and 4 mg/l) each alone or with all possible combination, between them (12 treatments). BRs at 1 mg/l gave the best results for bud height, diameter, fresh and dry weight reproductive leaves flower diameter, and number of flowers, while 4 mg/l of brassinostroid gave the highest chlorophyll content A, B, and total carbohydrate of petunia plants, stem diameter, flower number, flowering period, root length, and root number. The flower diameter, chlorophyll A, chlorophyll B, flowering duration, total carbohydrates, leaf area, and stem diameter were measured when gibberellic acid alone was applied at 200 mg/l. The best results were obtained when we used both barassinostroids and gibberellic acid at 1 mg/l of barassinostroids and at 100 mg/l of gibberellic acid, shoot high and flower diameter while using 4 mg/l of brasssinostroid with 100 mg/l of gibberllic acid for non–buds and flower diameter while 4 mg/l of brasssinostroid with 100 mg/l of gibberellic acid gave total carbohydrates, fresh weight and limited area, compared with other treatments.