WATER PERMEABILITY OF PLASMA-MEMBRANES OF CULTURED RICE, GRAPE, 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 fr om murine B-cell lymphoma was measured in the frequency range of 0.2 t o 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 trans itional changes in cell volume under external osmotic stress when sucr ose was added. From the course of volume changes with such stress, the mater permeabilities of the plasma membrane, L-p,, were measured to b e 0.015, 0.020, and 0.090 pm/(s.Pa) at 25 degrees C, for rice cells, g rape cells, and CH27 cells, respectively. The smaller L-p for plant ce lls seemed to explain why preservation of plant cells by freezing is m ore difficult than for animal cells. From the temperature dependence o f L-p, 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 .