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Plasma membrane was isolated from fresh cucumber (Cucumis sativus L.) roots and calli and the purity of separation was investigated through the measurement of ATPase activity and protein content. The induction of callus from cucumber root tissue was performed by the addition of NAA 3ppm and BA 0.5ppm to the 1/2 MS medium, and they were kept in the incubator set at 25 1℃ under the dark condition. Fresh root was taken from cucumber plant grown in nutrient film technique system supplied with Cooper´s nutrient solution. The ATPase activity of supernatant obtained from 1,500×g of cucumber root calli was not increased with the addition of Mg^(2+) and K^+. However, pellet from further centrifuge at the speed of 10,000×g did respond to the addition of such metal ions. Supernatant separated at 10,000×g was further centrifuged at 80,000×g, and the resulting pellet showed the metal-dependent ATPase activity. ATPase activity was decreased up to 50% by the addition of vanadate. Interface was collected from 30/42.9 % sucrose density gradient and centrifuged at the speed of 80,000×g for 2 hrs., which showed the higher metal dependent activity. And this implied the possibility of omission of dextran density gradient. The interface of 34/45% sucrose density gradient loaded with 15,000×g pellet showed the increase in 3 times of ATPase activity. The sensitivity of vanadate indicates the possibility of plasma membrane origin.
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