Plasmolysis is the Contraction of Protoplast due to Excessive Loss of Water
Plasmolysis is the loss of water by osmosis from a plant cell to the extent that the cytoplasm separates and shrinks away from the cell wall. This happens when the cell is placed in a solution that has a higher solute concentration than that of the cell sap, i.e. it has lower (more negative) water potential. When a plant cell is kept in a concentrated solution, water leaves the cell vacuole. As water leaves the vacuole the total volume of the cytoplasm decreases while the cell wall itself, being rigid, hardly changes. The external solution fills the space because cell wall is fully permeable for the solutions. When a plasmolyzed cell is kept in distilled water, the cell takes water and first becomes flaccid. Further entry of water causes it to become turgid. (Page 482)
© (From the Book, “Biology for Medical Entrance”, S Chand Publishing, New Delhi, India)
(a) Normal Plant cell, (b) Plasmolyzed plant cell .