The ameliorative effect of silicon and potassium on drought stressed grape (Vitis vinifera L.) leaves

The effect of sodium silicate (Si) and potassium (K) were investigated on the major antioxidant enzyme activities in two different grapevine cultivars (Vitis vinifera L., cvs Yezandai and Malinger Ramfi) under drought stress. The traits included superoxide dismutase (SOD, EC 1.15.1.1), catalase (CAT, EC 1.11.1.6), peroxidase (POD, EC 1.11.1.7), guaiacol peroxidase (GPX, EC 1.11.1.7), ascorbate peroxidase (APX, EC 1.11.1.11), and also physiological traits such as leaf water content ratio (LWCR), chlorophyll (Chl), soluble protein contents, hydrogen peroxide (H2O2), proline (Pro) and glycine betaine (GB) accumulation. The experiment was performed in a completely randomized design including four treatments i.e. the control, drought, Si-drought (0.004 M sodium silicate/kg soil), and K-drought (0.004 M potassium phosphate/kg soil) with three replications in a green house. Drought stress caused a considerable decrease in LWCR, chlorophyll and soluble protein contents. In contrast, compared with the plants treated with drought, applied Si and K significantly enhanced the activities of SOD, CAT, POD, GPX and APX. Under drought stress Pro and GB increased. The results indicated that Si and K offset partially the negative impacts of drought stress by increasing the tolerance of grapevine through rising antioxi- dant enzyme activities and osmotic adjustment.