Silicon alleviates salt stress in pistachio plants

In this work, the effects of silicon (Si) supplementation were studied in pistachio (Pistacia veraL. cv Ahmadaghaii) plants exposed to high salinity stress. Plants were grown in pots undercontrol and salt (EC=15 dS m-1) conditions without or with Si treatment (0.35 g Na2SiO3 Kg-1soil) 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 tothose without Si supply under salinity conditions. Salt stress caused a significant reduction ofleaf photochemical activities; however, Si application ameliorated these effects. The reductionof 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 androots was significantly reduced by Si, while root K and leaf Ca concentrations were higher inSi-treated plants under salt stress compared with –Si ones. The activity of antioxidativeenzymes increased under salt stress and Si application caused a further increase, beingsignificant for superoxide dismutase (SOD). Salt stress induced membrane damage, as wasindicated 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 Simediatedalleviation of salt stress in pistachio plants is related to higher photosynthesis andwater-use efficiency, a reduction of Na uptake and transport, and the stimulation of the plant’santioxidative defence capacity.