Selenium protects olive (Olea europaea L.) from drought stress

• Se increases photosynthesis, fruit yield and leaf water content.
• Leaf water content is not achieved by the inhibition of transpiration rate.
• Se increases the activities of some antioxidant enzymes.
• Se was effective in reducing the content of malondialdehyde in stressed trees.
• Se is effective in reducing the drought stress on olive (Olea europaea L.).

The aim of this study was to evaluate if Se could be effective in reducing the stress caused by drought on olive (Olea europaea L.). Young water-stressed trees (cv. Maurino) were treated with sodium selenate solutions (50 and 150 mg Se L−1) by foliar spray. Gas exchange, relative water content (RWC) and fruit yield were compared with well irrigated trees and stressed untreated trees. Furthermore, the activity of antioxidant enzymes ascorbate peroxidase (APX; EC 1.11.1.11), catalase (CAT; EC 1.11.1.6) and glutathione peroxidase (GPOX; EC 1.11.1.9) and the variations in the content of malondialdehyde (MDA) were investigated. The results indicated that under water stress, foliar application of Se could increase photosynthesis (PN) and fruit yield, regulate the water status of trees and maintain a sufficiently high level of leaf water content that was not achieved by the inhibition of transpiration rate (E), which instead was higher than that in water-stressed untreated trees. Se increased the activities of APX, CAT and GPOX, and reduced the content of MDA, which otherwise accumulated during oxidative perturbations. This research is the first that shows that Se application can improve olive resistance to drought, and more in general in a tree species, by protecting the cells from oxidative injuries and regulating water status.