Plasmolysis is due to

Plasmolysis is due to Exosmosis.
Plasmolysis is a typical response of plant cells exposed to hyperosmotic stress. The loss of turgor causes the violent detachment of the living protoplast from the cell wall.
As exosmosis is the movement of water molecules from within the cell to outside through a semipermeable membrane. This process ultimately causes shrinkage or plasmolysis of the cell.
The plasmolytic process is mainly driven by the vacuole. Plasmolysis is reversible (deplasmolysis) and characteristic of living plant cells.