Silicon alleviates salt stress in pistachio plants

In this work, the effects of silicon (Si) supplementation were studied in pistachio (Pistacia vera L. cv Ahmadaghaii) plants exposed to high salinity stress. Plants were grown in pots under control and salt (EC=15 dS m-1) conditions without or with Si treatment (0.35 g Na2SiO Kg-1 soil) under field conditions. Salt stress reduced the plants’ growth significantly in both –Si and +Si plants; however, Si-supplied plants had a higher root and shoot dry weight as compared to those without Si supply under salinity conditions. Salt stress caused a significant reduction of leaf photochemical activities; however, Si application ameliorated these effects. The reduction of the net CO2 assimilation rate under salinity stress was alleviated by Si application, accompanied by an increase in water-use-efficiency. The concentration of Na in the leaves and roots was significantly reduced by Si, while root K and leaf Ca concentrations were higher in Si-treated plants under salt stress compared with –Si ones. The activity of antioxidative enzymes increased under salt stress and Si application caused a further increase, being significant for superoxide dismutase (SOD). Salt stress induced membrane damage, as was indicated by a higher malondialdehyde (MDA) concentration. In Si-supplemented plants, however, the MDA amount did not increase under salt stress. The results indicated that the Simediated alleviation of salt stress in pistachio plants is related to higher photosynthesis and water-use efficiency, a reduction of Na uptake and transport, and the stimulation of the plant’s antioxidative defence capacity.