Abstract:The electron microscopical observations using Cytochemical method of cerium phosphate precipitation indicated that the Ca2+-ATPase activity was mainly localized at the plasmalemma in wheat seedling cells grown at normal temperature. And the enzyme activity did not appear to be different between water-soaked and CR4-Soaked treatments under normal temperature. However, the differences occurred when wheat seedlings were treated for 12 hrs and 24 hrs at - 7℃: the plasmalemma Ca2+-ATPase activity in the seedlings from water-soaked seeds was markedly decreased, and the ultrastructures were disrupted, and that from cold-resistant agent CR4-Soakod seeds was still maintained, and their free structures were also intact. The results suggest that the cold-resistant agent CR-4 plays an important role for stabilizing plasmalemma calcium pump (Ca2+-ATPase) under low temperature stress.