Proton pumps play an important role in the physiological activities of plants. Changes in membrane-associated H + - and Ca 2+ -ATPase activities in heat-shocked plants after heat acclimation (HA) or salicylic acid (SA) pre-treatment in annual young grape plants (Vitis vinifera L. cv. Jingxiu) were investigated. ATPase activity was assayed through biochemical analysis in which two-phase partitioning was used to purify plasma membranes and cerium trichloride was precipitated with an electromicroscopic cytochemical method. The plasmalemma H + - and Ca 2+ -ATPase activities were higher in HA- or SA-pre-treated plants than in controls. The stability of H + - and Ca 2+ -ATPase activities in pre-treated plants always remained at higher levels during subsequent heat shock treatment, which was consistent with the observations made using an electromicroscope. A number of cerium phosphate grains representing enzyme activity in HA- or SA-pre-treated plants were observed 6h following heat shock, whereas no grains were found in control plants under the same conditions. These results suggest that the changes in the activities of plasma membrane H + - and Ca 2+ -ATPase contributed to the thermotolerance induced by either HA or SA pre-treatment in young grape plants and the two pre-treatments may have had the some same regulatory mechanism.