ABSTRACT
Freezing injury in plants is a consequence of membrane destabilization. Although all cellular membranes are vulnerable to freeze-induced destabilization, stability of the plasma membrane is of critical importance because of the central role that it plays during a freeze/thaw cycle. Cryomicroscopic studies of isolated protoplasts during a freeze/thaw cycle and electron microscopic studies of the protoplasts subjected to osmotic excursions have revealed that the plasma membrane of non-acclimated protoplasts undergoes endocytotic vesiculation during osmotic contraction. The lipid composition of the plasma membrane of rye leaves is unique in comparison with other plant cell membranes, though similar to the tonoplast. The molecular mechanisms by which membrane destabilization is effected differ depending on the freeze/thaw protocol and the freezing tolerance of the specimen. Elucidation of these mechanisms has provided a foundation to consider the role of membrane lipid alterations during cold acclimation and the increased cryostability of membranes.
