SALICYLIC ACID ALLEVIATES SALT STRESS IN SOYBEAN BY IMPROVING ANTI-OXIDANT CAPACITY AND GROWTH PERFORMANCE

The paper investigated the effects of salicylic acid (SA, 0, 0.5, and 0.75 mM) on soybean (Glycine max) development, antioxidant enzyme activity, and biochemical characteristics under salt stress. The results showed that, salinity exposure (0, 25, 75, and 125 mM NaCl) inhibited soybean growth by lowering the fresh weight of the shoot and root, inhibiting leaf development, and triggering necrosis on old leaves. With 125 mM NaCl level, lipid peroxidation or hydrogen peroxide (H2O2) production rose by 3.37 and 2.54, respectively, whereas membrane stability decreased, which was alleviated by the addition of SA. Compared with the control, SA (0.5 mM) considerably boosted growth. Salinity (125 mM NaCl) stress increased proline accumulation by 4.63 times, carbohydrates by 39.61 percent, free amino acids via 9.44 percent, and protein content via 7.91 percent, all of which were further promoted by SA, indicating a greater stress adaption. Application of SA increased the activity of antioxidant enzymes including SOD, CAT, and APX by 1.76, 2.25, and 2.22 times, respectively, resulting in improved reactive oxygen species removal and protection from oxidative stress. Furthermore, excessive Na+ uptake in salinity-stressed plants inhibited K+ absorption and triggered leaf necrosis, while application of SA significantly reduced the damage. These results suggested salt stress has a negative impact on soybean growth and development and supplementing with a suitable dose of SA alleviated the detrimental effects by modulating osmolyte levels, antioxidant enzyme activity, and critical element intake.