Growth Control of Hibiscus Pot Plants by Foliar Spraying With Paclobutrazol and Two Sources of Potassium

Abstract

In a trial to get an ideal growth of Hibiscus rosasinensis cv. Cooperi, a factorial pot experiment was carried out at the Botanical Garden of the National Gene Bank, Agricultural Research Center, Giza, Egypt during 2020 and 2021 seasons. Foliar spraying with both paclobutrazol (PBZ) at different levels (0, 50, 100 and 150 ppm) and two sources of potassium (K-sulfate at 1.5 and 3.0 g/l and K-humate at 2.0 and 4.0 g/l) and their interactions were applied. Vegetative growth, flowering parameters and some chemical constituents were evaluated. The results indicated that increasing PBZ level resulted in the lowest values for most studied parameters except PBZ at 100 ppm as recorded the highest values of number of leaves, branches and flowers/plant, vegetative growth fresh and dry weights, chlorophylls (a and b), carotenoids and indoles. Foliar spraying with two potassium sources was superior to control (without potassium foliar spraying) as recorded higher values. Integration of potassium foliar spraying reversed the undesirable effects of spraying with PBZ alone in particular at the high levels. The mastery was to PBZ at 100 ppm + K-humate at 2.0 g/l as recorded the highest values in most cases i.e. number of leaves, branches and flowers/plant, vegetative growth fresh and dry weights, chlorophylls (a and b), carotenoids and indoles. To produce high-quality Hibiscus rosa-sinensis cv. Cooperi pots, it is advised to treat the plants with PBZ at 100 ppm + K-humate at 2.0 g/l for 6 times at 2-week intervals.