The Intracellular Pressure of Nitella in Hypertonic Solutions and Its Relationship to Freezing Injury

摘要

Giant cells of the alga Nitella flexilis show a resistance to hypertonic dehydration, according to an interpretation of measurements of intracellular pressure. As the osmolality of the bathing medium is increased, turgor pressure drops to zero at a rate predicted by the Boyle-van't Hoff relationship, and then goes below atmospheric pressure at a rate of 0.09 atmosphere per osmolal. Membrane failure occurs by about 2.5 times the isotonic concentration of the cell. The 0.05 atmosphere pressure gradient at 2 times isotonicity implies the coexistence of a 2.5 milliosmolal gradient at the temperature of the experiments, with the interior of the cell at a lower concentration. We interpret this as an indication that the Nitella cell resists the loss of intracellular water. (Author)