Impact of Growth Regulating Substances on Different Varieties of Okra (Abelmoschus esculentus L.)

Abstract

India, the world’s second-largest vegetable producer (204.96 million tonnes annually), dominates okra cultivation, with Gujarat leading (1.132 million tonnes in 2023–24). This study investigated the interaction between plant growth regulators (PGRs) and high-yielding okra varieties, the suitability of varieties for southwestern Punjab’s agro-climate and the efficacy of gibberellic acid (GA₃), indole-3-acetic acid (IAA), and naphthalene acetic acid (NAA) in improving growth and yield. A field study was conducted during the summer season of 2023–2024 at Guru Kashi University, Punjab, India, to evaluate the impact of plant growth regulators (PGRs) on four okra varieties: Varsha Uphar, Unnat Hisar, Hisar Naveen, and Kashi Chaman. The experiment employed a split-plot design with three replications, assigning varieties to main plots and ten PGR treatments to subplots. Treatments included combinations of gibberellic acid (GA₃: 200, 300, 400 ppm), indole-3-acetic acid (IAA: 10, 15, 20 ppm), naphthalene acetic acid (NAA: 10, 20, 30 ppm), ascorbic acid (250 ppm), and a control. Results demonstrated that IAA at 20 ppm + ascorbic acid (250 ppm) significantly enhanced vegetative growth, flowering, and yield parameters. Unnat Hisar treated with IAA 20 ppm + ascorbic acid recorded the highest plant height (9.28 cm at 25 DAS), internodal length (4.84 cm), and branches (20.6). Varsha Uphar, under the same treatment, achieved the tallest plants at harvest (102.5 cm), maximum leaves (21.88), fruits per plant (22.3), fruit length (13.44 cm), and yield (158.4 q/ha). The earliest flowering occurred in Hisar Naveen with NAA 10 ppm (35.13 days). The synergistic effect of IAA and ascorbic acid optimised growth and yield, particularly in Varsha Uphar and Unnat Hisar, establishing this combination as highly effective for okra cultivation in semi-arid regions.