Antioxidative enzymes in wheat subjected to increasing water deficit and rewatering

Two cultivars of wheat seedlings differently sensitive to drought (cv. Adam ello more sensitive than cv. Ofanto) were subjected to water depletion and rehydration. Cv. Ofanto showed a higher relative water content in compariso n with cv. Adamello during the whole stress period. Soluble and thylakoid-b ound activities of ascorbate peroxidase (APX) and superoxide dismutase (SOD ) showed different behaviours in the two cultivars. Differently from the se nsitive 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 sen sitive cultivar contained the double amount of soluble APX in comparison wi th the tolerant one and the activity of the enzyme was induced when a moder ate water stress intensity was reached. As for APX, SOD and dehydroascorbat e reductase (DHAR) activities were also higher in the sensitive cultivar, w hile thylakoid-bound SOD decreased ail over the stress period. The electrop horetic pattern of the soluble extract showed at least 3 isozymes of SOD, 4 isozymes of APX and 2 isozymes of DHAR.