Effects of exogenous spermidine on lipid peroxidation and membrane proton pump activity of cucumber seedling leaves under high temperature stress. Effects of Exogenous Salicylic Acid on Ion Content,Activities of ATPase and PPase of the Roots in Chrysanthemum Under Salt Stress Effects of Exogenous Salicylic Acid on Ion Content,Activities of ATPase and PPase of the Roots in Chrysanthemum Under Salt Stress