Lamellar-to-hexagonal sub(II) phase transitions in the plasma membrane of isolated protoplasts after freeze-induced dehydration

In protoplasts isolated from nonacclimated rye leaves (Secale cereale L. cultivar Puma), cooling to -10 degree C at a rate of 1 degree C/min results in extensive freeze-induced dehydration (osmotic contraction), and injury is manifested as the loss of osmotic responsivess during warming. Under these conditions, several changes were observed in the freeze-fracture morphology of the plasma membrane. These included lateral phase separations in the plasma membrane, aparticulate lamellae lying next to the plasma membrane, and regions of the plasma membrane and associated lamellae in various stages of lamella-to-hexagonal sub(II) transition.