Abstract: The aqueous two-phase partition method was used to isolate and purify plasma membrane (PM) vesicles from mung bean hypocotyls. The PM vesicles were purified well when the proportion of the weight of hypocotyls and two-phase partition reached 32:8. Bovine serum albumin in homogenization medium influenced the latency activity of the PM H+-ATPase. The enzyme hydrolysis activity was Mg2+ dependent and was strongly stimulated by Ca2+. Fusicoccin (FC), an activator of PM H+-ATPase, stimulated the enzyme activity with the maximal increase of 72% in vivo and of 30% in vitro as compared with control.