Effect of Silicon on Antioxidant Enzymes Activities and Osmotic Adjustment Contents in Two Bread Wheat Genotypes under Drought Stress Conditions

Silicon is the second most prevalent element within the soil and it has beneficial effects to enhancing the tolerance of plants to biotic and abiotic stresses. To study the effect of silicon on drought stress in Vee/Nac and Pishtaz bread wheat (Triticum aestivum L.) genotypes, a factorial experiment was performed in a completely randomized design with three treatments including control, drought and silicon-drought (2 mmol silicate sodium kg-1) and three replications in green-house. Proline and glycine betaine contents, the activities of the antioxidant enzymes including catalase, (CAT), superoxide dismutase (SOD), ascorbate peroxidase (APX), peroxidase (POD) and relative water content (RWC), chlorophyll and leaf total soluble protein content were measured and evaluated . Results indicated that silicon partially offset the negative impacts of drought stress and increased tolerance by rising SOD, CAT, APX and POD activities and soluble protein content in both genotypes. In contrast, drought stress considerably decreased RWC, chlorophyll and soluble protein content. No significant difference was observed in CAT activity between the “drought” and “control” treatments in both genotypes. Result also showed that Si treatment increased proline and glycine betaine contents. The effect of silicon was observed to be higher in Vee/Nac than Pishtaz. It can be concluded that the role of silicon in drought tolerance of wheat genotypes was associated with the increase in antioxidant enzymes activities, therefore, alleviating oxidative damage induced by over producing reactive oxygen species under drought stress and protecting many physiological processes of stressed plants.