Abstract:The effects of LaCl3 on membrane permeability and the secretion of proton of the root segments of corn (Zea mays L.) “Jing Zhao No. 8” were studied, and the process of K+ exudation was analyzed by means of kinetic method. The exudate conductivity and leakage of K+ and sugar were lowered, and proton secretion was enhanced by LAC18 treatments in corn root segments. Kinetic analysis of K+ exudation illustrated, that (1) mathematical model used for absorption study was suitable for study of exudation process, (2) the maximum absorption rate (Vmax) was increased and Michaelis constant was unchanged in presence of LaCl3 and/or CaCl2, (3) the lowering of K+ leakage was due to the increased Vmax in presence of LaCl3 and/or CaCl2.