Abstract:The tomato calli were grown on the MS media supplemented with differen.t kinds of exogenous hormones respectively and the protoplasts were isolated from them after subculturing for 3 times. The concanavalin A (Con A) binding capacities of plasma membranes prepared from the protoplasts were compared by using radiochemical assay with 125I-Con A. The result shows that Con A reactivity of plasma membrane is greatly increased by 2,4-D (2 mg/l) treatment and the other growth substances affect on Con A binding capacity variously.