Water permeability of plasma membranes of cultured rice [Oryza sativa], grape [Vitis], and CH27 cells measured dielectrically

The capacitance of suspensions of cultured rice cells (Oryza sativa L. ssp. japonica), grape cells (Vitis sp.) and CH27 cells originated from murine B-cell lymphoma was measured in the frequency range of 0.2 to 10 MHz. The relationship between the increase in capacitance caused by the presence of cells at 0.4 MHz, delta-C, and the cell density was linear. Measurement of capacitance was useful in measurement of transitional changes in cell volume under external osmotic stress when sucrose was added. From the course of volume changes with such stress, the water permeabilities of the plasma membrane, Lp, were measured to be 0.015, 0.020 and 0.090 pm/(s.Pa) at 25 degrees C, for rice cells, grape cells, and CH27 cells, respectively. The smaller Lp for plant cells seemed to explain why preservation of plant cells by freezing is more difficult than for animal cells. From the temperature dependence of Lp, the apparent activation energies were calculated to be 12.0 +- 2.9 and 13.0 +- 5.2 kcal/mol for rice cells and CH27 cells, respectively