Plasmolyse

Plasmolysis is a cellular phenomenon in which the cytoplasm shrinks away from the cell wall due to loss of water through osmosis, typically occurring in plant cells exposed to hypertonic solutions. As water leaves the cell, the plasma membrane pulls inward from the cell wall, creating spaces around the vacuole and cytoplasm while the rigid cell wall remains intact. In incipient plasmolysis the detachment begins at localized areas, whereas complete plasmolysis involves most or all of the membrane detaching from the wall.

Cause and mechanism: Plasmolysis occurs when the external solution has a higher solute concentration than the cell interior, causing water to move out of the cell. The reduction in turgor pressure allows the plasma membrane to separate from the cell wall. The process is typically reversible if the cell is returned to a suitable, less concentrated environment; water re-enters the cytoplasm, the membrane reattaches to the wall, and turgor pressure is restored. Prolonged exposure or severe dehydration can cause irreversible damage or cell death.

Significance and observations: Plasmolysis is a classic demonstration of osmosis and cell-wall–membrane interactions. It is commonly observed in plant tissues and cultured cells treated with hypertonic solutions, such as Elodea or onion epidermal cells in laboratory settings. The phenomenon helps illustrate differences between plasmolysis and other forms of cell damage, such as cytolysis, where the cell contents break apart rather than pull away from the wall. Plasmolysis also has relevance to plant responses to salinity and drought stress, reflecting how cells regulate water balance.