Increase in tension at the surface of protoplast as a sign of cell wall formation inBoergesenia forbessi

Protoplasts prepared from thalli ofBoergesenia forbesii were subjected to the measurement of tension at the surface by means of the suction method. The tension at the surface just after completion of spheration was 0.2–0.4 dyne/cm irrespective of the temperature. Since this value is of the same order of magnitude as those measured in other species of cells without a cell coat, it is suggested that the protoplast just after spheration is covered with the plasma membrane. The measured tension at the surface was constant and not affected by the degree of deformation of the protoplast, suggesting that the surface of the protoplast is not elastic. After some time the tension began to increase abruptly. Both the latent time elapsed prior to the increase in the tension and the rate of tension increase were strongly dependent on the temperature. As long as protoplasts were treated with cellulase, increase in the tension was completely inhibited, but it occurred soon after washing out of the cellulase. Protoplasts were stained with Calcoflour White at around the time when the tension began to increase. These results suggest that the cell wall formation begins at the time of abrupt increase in the tension at the surface.