Age induced changes in cellular membranes of imbibed soybean seed axes [free radicals, phase properties]

The physical and chemical properties of microsomal membranes and cellular antioxidant systems were investigated in imbibed soybean (Glycine max L. Merr. cv. Maple Arrow) seeds following aging for 5 years at room temperature. The loss of germination capacity in aged seeds was associated with increased solute leakage during imbibition and with a loss of membrane phospholipid. Higher levels of free fatty acids were observed in the microsomal membranes from aged seeds. However, there was no change in fatty acid saturation. Wide angle X‐ray diffraction studies indicated the presence of gel phase in addition to liquid‐crystalline phase lipid domains in the membranes of aged seeds. Those from fresh seeds were exclusively liquid‐crystalline. Fluorescence depolarization, using diphenylhexatriene, suggested that the microviscosity of the membrane bilayer was increased by aging. Aged seeds had a lower antioxidant potential in the lipid fraction, lower tocopherol content, and reduced ascorbate:dehydroxyascorbate ratio indicating that the aging process was associated with exposure to an oxidative stress.