Antioxidant Response to NaCl Stress in Salt‐Tolerant and Salt‐Sensitive Cultivars of Cotton

The mechanism(s) importing salt tolerance to plants remains unresolved. Although cotton ( Gossypium hirsutum L.) is classified as salt‐tolerant plant, variation in salt tolerance has been observed among different cultivars. The purpose of this study was to determine if more salt‐tolerant cultivars contain higher constitutive or inducible levels of antioxidants than more salt‐sensitive cultivars. Greenhouse‐grown salt‐tolerant (cv. Acaia 1517‐88 and Acala 1517‐SR2) and salt‐sensitive (cv. Deltapine 50 and Stoneville 825) cotton plants treated with either 0 or 150 m M NaCl were analyzed for differences in growth and antioxidant capocities. The 150 m M NaCl treatment resulted in more than 40% reduction in growth of Deltapine 50 and Stoneville 825 and less than 30% reduction in the Acala cultivars. The more salt‐tolerant cultivars had higher constitutive levels of catalase (121‐215%) and u‐tocopherol (312‐420%). The salt treatment resulted in a 38 to 72% increase in peroxidase activity and a 55 to 101% increase in glutathione reductase activity in the Acala cultivars while the activities of these enzymes remained constant or decreased in the more sensitive cultivars. The Acala cultivars also exhibited a lower oxidized/reduced ascorbic acid ratio and a higher reduced/oxidized glutathione ratio than the more sensitive cultivars when grown at 150 m M NaCl. When subjected to a one‐time salt treatment, lipid peroxidation in Deltapine 50 increased 51% over Acala 1517‐88. These data indicate that protection from oxidative damage by higher levels of antioxidants and a more active ascorbate‐glutathione cycle may be involved in tbe development of salt tolerance in cotton.