• Osmosis is the?net movement of water molecules?from a region of?higher water potential?(dilute solution) to a region of?lower water potential?(concentrated solution), through a partially permeable membrane
• If a plant cell is placed in?pure water?or a?dilute solution, water will?enter?the plant cell through its partially permeable cell surface membrane by?osmosis, as the pure water or dilute solution has a?higher water potential?than the plant cell
• As water enters the?vacuole?of the plant cell, the?volume?of the plant cell?increases
• The expanding?protoplast?(living part of the cell inside the cell wall) pushes against the cell wall and?pressure builds up?inside the cell – the inelastic cell wall prevents the cell from bursting
• The pressure created by the cell wall also stops too much water entering and this also helps to prevent the cell from bursting
• When a plant cell is fully inflated with water and has become rigid and firm, it is described as fully?turgid
• This turgidity is important for plants as the effect of all the cells in a plant being firm is to provide?support?and?strength?for the plant – making the plant stand upright with its leaves held out to catch sunlight
• If plants do not receive enough water the cells cannot remain rigid and firm (turgid) and the plant?wilts

Osmosis of water into a plant cell

• If a plant cell is placed in a solution with a?lower water potential?than the plant cell (such as a concentrated sucrose solution), water will?leave?the plant cell through its partially permeable cell surface membrane by?osmosis
• As water leaves the?vacuole?of the plant cell, the volume of the plant cell?decreases
• The protoplast gradually shrinks and no longer exerts pressure on the cell wall
• As the protoplast continues to shrink, it begins to pull away from the cell wall
• This process is known as?plasmolysis?– the plant cell is?plasmolysed

Plasmolysis of a plant cell that has been placed in a solution with a lower water potential than the cell itself