Cellular expansion at low temperature as a cause of membrane lesions.

Rates of solute leakage from excised discs of cucumber (Cucumis sativus L. cv Straight Eight) cotyledons were altered by temperature during plasmolysis in the manner of a simple diffusion phenomenon; the log of the leakage rate increased in proportion to the temperature. During deplasmolysis, however, leakage rates responded to temperature with a very different pattern: chilling conditions (below about 20 degrees C) caused large increases in leakage rates, indicating disruption of membrane integrity in the tissues. The time course of restoration of normal leakage rates after deplasmolysis/chilling damage indicated a rapid repair of the lesions. A similar sensitivity to low temperatures was found during rehydration after leaf desiccation, with low temperatures again causing high leakage rates. It is suggested that low temperatures interfere with membrane expansion, possibly by lowering elasticity and hindering the incorporation of lipid material into the expanding membrane. The expansion of tissues at low temperatures may cause lesions in cellular membranes, contributing to chilling injury.