Phytochemical responses and antioxidant activity of potassium-treated grapevines (Vitis vinifera L.) in salinity stress condition

Supplemental nutrition through affecting both enzymatic and non-enzymatic protective systems can modulate the oxidative stress induced by salinity. In this study the interaction effect of foliar application potassium (0 and 1.5% potassium sulfate; PS) and salinity (0, 25, 50 and 100 mM sodium chloride) on membrane degradation indices, phytochemical responses and antioxidant enzymes activities and also leaves nutrient elements of Bidaneh-Sefid grapevine was investigated as a factorial experiment based on a completely randomized design. By increasing salinity, hydrogen peroxide and malondialdehyde were increased in vines leaves under salinity stress. However the application of PS at 1.5% decreased the concentration of these indices 20 and 26 percentage respectively. As the salinity increased, the phenolic and flavonoid content of the leaves increased in the vines, however, foliar application of PS at 1.5% increased their content at the higher level in PS-treated vines. Moreover, in PS- treated vine at 1.5% soluble proteins increased dramatically even in high NaCl levels. Catalase and ascorbate peroxides activity increased until 50 Mm salinity stress, while with PS at 1.5% treated vine, the activities of these enzymes increased until 100 Mm NaCl. Potassium application also increased these enzymes activities at all levels of salinity. Also, the interaction of salinity and PS increased guaiacol peroxidase activity. Iron, zinc and leaf manganese concentrations increased due to the interaction of salinity and potassium. Totally, PS through the accumulation of soluble proteins, flavonoids and phenol, as well as increasing the activity of antioxidant enzymes finally reduced the oxidative stress induced by salinity in the vines leaves.