What happens when plasmolysed spirogyra filament is put in water?

When a plasmolysed Spirogyra filament is put in water, the cell membrane will rehydrate and regain its original shape. The water will move into the cell through osmosis, causing the cell to become turgid again. This process is known as deplasmolysis, where the protoplast swells and pushes the cell membrane against the cell wall.