Alteration of Liposomal Membrane Fluidity by Gibberellic Acid

Abstract

Lipid bilayers (liposomes) with many characteristics of natural membranes exhibit thermal transitions. The transition point can be determined experimentally from the rates of leakage of glucose through the lipid barrier at various temperatures. In response to treatment with gibberellic acid or diethylstilboestrol, the permeability of the liposome to glucose is increased; in addition, the temperature at which the transition occurs is shown to be inversely proportional to the gibberellic acid concentration. The consequences of increased fluidity in the membrane, brought about by the hormone, are discussed. The hypothesis is advanced that the membrane could be the primary target for hormonal action in plants.