Modulation of Antioxidant Enzyme Activities by Silicon Application in Sorghum Under Drought Stress Conditions

초록

Drought stress represents a major threat to global agricultural productivity, particularly affecting cereal crops such as Sorghum bicolor (L.) Moench. This study investigated the role of silicon (Si) in alleviating drought-induced oxidative stress through the modulation of antioxidant enzyme activities in sorghum seedlings. Using a drought-tolerant Sudanese cultivar (cv. Gadambalia), plants were treated with sodium silicate (1.67 mM) and subjected to osmotic stress via sorbitol treatment. Hydrogen peroxide (H₂O₂) levels were significantly elevated under drought stress, reaching 3.48-fold and 8.00-fold increases in shoots and roots, respectively. Si application substantially reduced H₂O₂ accumulation to 1.95-fold and 3.81-fold in shoots and roots. Enzyme activity analysis revealed that ascorbate peroxidase (APX) remained relatively stable across treatments, while catalase (CAT) showed a sparing effect under Si application. Peroxidase (POD) activity remained elevated in Si-treated plants under stress, indicating maintained antioxidant defense capacity. These results demonstrate that Si mitigates drought-induced oxidative stress not only through enzymatic regulation but primarily by reducing primary ROS generation, thereby enhancing plant stress tolerance and growth performance under water-deficit conditions.

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