Abstract:A method for the isolation of plasma membrane enriched fraction from plant sources is described. An aqueous two-phase system is suitable for the isolation of plasma membrane. Purified plasma membrane fractions have been prepared from Vicia faba leaves and pollen tubes of Luffa cylindrica. The determination of marker enzymes shows that the plasma membrane has a high affinity for the polyethylene glycol-rich upper phase, whereas those membranes from mitochondria, chloroplasts and other organelles prefer the dextran-rich lower phase and the interface. The plasma membrane was identified with the aid of silicotungstic acid-chromic acid staining. In the upper phase there are mainly stained elliptical vesicles, whereas in the lower phase there are many differnet kind of unstained vesicles. This result is coincident with the marker enzyme examination. The two-phase method for the isolation of plasma membrane may be widely applied not only to nongreen tissues but also to green tissues of plants.