Alleviation of drought stress by silicon supplementation in pistachio (Pistacia vera L.) plants

The effect of silicon (Si) supplementation (0.35 g Na₂SiO₃ kg-1 soil, 2.73 mmol Si kg^-1 soil) was studied in drought-stressed pistachio (Pistacia vera L. ‘Ahmadaghaii’) plants under field conditions. Silicon treatment significantly increased plant dry weight and relative water content under drought stress. The application of Si for drought-stressed plants improved the maximum quantum yield of PSII. A reduction in the net assimilation rate due to drought stress was alleviated by Si application, accompanied by an increase in stomatal conductance. Silicon treatment resulted in higher catalase and superoxide dismutase activities and lower lipid peroxidation in the leaves of drought-stressed plants. The results suggest that supplementation of water-deficient pistachio plants with Si alleviates the adverse effects of drought due to its enhancement of photochemical efficiency and photosynthetic gas exchange, as well as an activation of the antioxidant defence capacity in this species.