ABSTRACT
This study investigated the physiological responses of Glycine max TGX 1448-2E soybean under drought stress and evaluated the effectiveness of plant growth regulators (PGRs), specifically salicylic acid (SA) and 2,4-dichlorophenoxyacetic acid (2,4-D), in mitigating these effects. Given soybean’s agricultural importance in Nigeria and the increasing threat of drought, this research aimed to enhance crop resilience. A controlled screen-house experiment at the Department of Plant Biology and Biotechnology, exposed soybean to varying drought stress levels (5%, 10%, and 30% moisture), control with enough watering, control with PGR and three concentrations of SA and 2,4-D treatments (5, 10, and 30 ppm). Physiological and biochemical analyses over 12 weeks measured chlorophyll content, antioxidant enzyme activities (SOD, CAT), protein content, and stress markers like proline and ascorbic acid. Drought stress reduced chlorophyll, protein levels, and photosynthetic efficiency while increasing oxidative stress markers. However, SA and 2,4-D at 5–10 ppm improved plant growth under drought. SA enhanced photosynthetic efficiency and antioxidant activity, while 2,4-D promoted height and reduced wilting. Moderate SA and 2,4-D (5–10 ppm) are recommended for improving soybean drought tolerance and yield in water-scarce regions like Nigeria. Further research should optimize application methods, assess long-term effects in field conditions, and explore their role in sustainable soybean production.
