Physiological Response of Glycine Max L. (soybean) Variety Tgx 1440-1e Under Drought Ameliorated by Plant Growth Regulators.

This study examined the physiological response of soybean (Glycine max L.) variety TGX 1440-1E to drought stress and the role of plant growth regulators (PGRs) in mitigating its effects. Conducted in the screen house of the Department of Plant Biology and Biotechnology, University of Benin, the research lasted twelve (12) weeks, assessing growth, photosynthetic efficiency, and yield. Four treatments were applied: control (well-watered), control with PGRs, drought-stressed and drought-stressed with PGRs. This was carryout at 3 concentrations of water calculated with the water holding capacity obtained from the soil and with PGRs (2,4-Dichlorophenoxyacetic acid and Salicylic acid) at three concentrations: 5ppm, 10ppm, and 30ppm. Key physiological parameters measured included chlorophyll, carotenoid, lycopene, enzymatic activities (superoxide dismutase and catalase), protein, ascorbic acid, and proline content. Growth and yield attributes such as plant height, leaf area, pod number, and seed weight were also evaluated. Drought stress significantly reduced chlorophyll, carotenoid, lycopene content, and antioxidant enzyme activity, while increasing protein, ascorbic acid, and proline accumulation. Weekly application of PGRs improved drought tolerance, enhancing biomass and seed yield. However, high PGR concentrations negatively affected chlorophyll, lycopene, and antioxidant enzyme activity, suggesting oxidative damage. Overall, the results indicate that moderate application of Salicylic acid effectively mitigates drought stress, improving the physiological and agronomic performance of TGX 1440-1E under water-limited conditions. This highlights the potential of PGRs in sustainable soybean production under drought stress.