Antioxidative enzymes in wheat subjected to increasing water deficit and rewatering

Two cultivars of wheat seedlings differently sensitive to drought (cv. Adamello more sensitive than cv. Ofanto) were subjected to water depletion and rehydration. Cv. Ofanto showed a higher relative water content in comparison with cv. Adamello during the whole stress period. Soluble and thylakoid-bound activities of ascorbate peroxidase (APX) and superoxide dismutase (SOD) showed different behaviours in the two cultivars. Differently from the sensitive cultivar, in which thylakoid-bound APX was induced as soon as water deficit was imposed, in the tolerant wheat the activation of the thylakoid-bound APX occurred only at high stress intensity. Controls of the more sensitive cultivar contained the double amount of soluble APX in comparison with the tolerant one and the activity of the enzyme was induced when a moderate water stress intensity was reached. As for APX, SOD and dehydroascorbate reductase (DHAR) activities were also higher in the sensitive cultivar, while thylakoid-bound SOD decreased ail over the stress period. The electrophoretic pattern of the soluble extract showed at least 3 isozymes of SOD, 4 isozymes of APX and 2 isozymes of DHAR.