BEHAVIOR OF PROTOPLASM FOR SURVIVAL IN INJURED CELLS OF VALONIA-VENTRICOSA - INVOLVEMENT OF TURGOR PRESSURE

By injuring cells of Valonia ventricosa, one of two survival strategie s - wound-healing and protoplast formation - is induced. The present s tudy revealed that turgor pressure, as well as Ca2+ in bathing medium, is involved in the choice between these survival strategies. On the p rocess of wound-healing, turgor pressure is recovered in the presence of both the wound plug, which closes the wound immediately after an in jury, and the aggregation of protoplasm around the wound, which serves to protect the inflow of outer medium into the protoplasm layer and a lso to strengthen the wound plug. When the size of the wound is more t han 150 mum in diameter, the protoplasmic aggregate strengthen the wou nd plug incompletely and, as a result, wound-healing is unsuccessful. In this case, the ejection of vacuolar sap is repeated, due to partial restoration of turgor pressure. In each ejection, the wound plug is b lown off, together with the aggregated protoplasm and, after several e jections are repeated, the cell is unable to heal the wound because of a lack of protoplasm around the wound. Continuous depression of turgo r pressure, during the repeat of the unsuccessful wound-healing, induc es disorganization of the protoplasm layer. Under these conditions, th e centrifugal propagation of protoplasmic aggregation, followed by the protoplasts formation, takes place easily. Effects of turgor pressure and Ca2+ in the bathing medium upon the wound healing is discussed an d the cytoplasmic behavior for survival of wounded cells is presented schematically.