The Effect of Calcium on the Salicylic Acid-Induced Thermotolerance in Young Grape Plants (Vitis vinifera L.) and Is Associated with Ca²+-ATPase in Plasma Membrane

The ´Jingxiu´ young grape plants (Vitis vinifera L. cv. Jingxiu) were used as materials to study the effects of calcium (Ca²⁺) on the salicylic acid (SA)-induced thermotolerance in young grape plants and was associated with Ca²⁺-ATPase in plasma membrane. The results showed that the SA-induced thermotolerance of plants pretreated with a Ca²⁺ chelator EGTA, a plasmalemma Ca²⁺ channel blockers La³⁺and the calmodulin (CaM) antagonist W7 was markedly weakened. Interestingly, CaM level was correlated well with SA or Ca²⁺ level in young grape plants. Ca²⁺-ATPase activity was assayed through biochemical and electromicroscopic-cytochemical method. Finally, the results were almost verified as identity in activity and distribution level. After the young plants were pretreated with heat acclimation or SA, the activity of the plasmalemma ^Ca2+-ATPase was higher than control. Meanwhile, the stability of ^Ca2+-ATPase activity of plants pretreated with heat acclimation or SA was enhanced under following heat shock. Through the observation of electromicroscope, the enzyme activity after heat acclimation or SA pretreatment was found to remain active 6h following heat shock, but the activity of each control was completely inactive. These results suggested that the thermotolerance induced by heat acclimation or SA was related to the activity of Ca2+-ATPase in plasma membrane.