Dehydration Injury and Resistance

The causes of dehydration of cells are evaporation, frost, and the osmotic action of hypertonic solutions. In addition to loss of water and consequent diminution of cell volume, there are other effects peculiar to the respective agencies, so that we cannot assume on theoretical grounds that the injury which each of them may cause is effected in the same way. One type of frost injury indeed has no counterpart in the action of drought or hypertonic solutions; namely, disruption of the protoplasm by intracellular ice formation. This, however, occurs only under rather special conditions and at the moment of freezing. It is usually fatal to hardy as well as tender cells. The protection which is developed against intracellular freezing on hardening is an increase of cell permeability which tends to prevent its occurrence (7, 8). This type of freezing is necessarily absent when marked resistance is displayed. Usually ice forms in the intercellular spaces and it is possible that here too it may produce injury otherwise than by dehydration.