In plasmolysis, the diameter of the vacuoles shrinks as water leaves the plant cell. This is because plasmolysis is the process where the cytoplasm separates from the cell wall due to water loss.
Understanding Plasmolysis and the Vacuole
Plasmolysis occurs when a plant cell is placed in a hypertonic solution (a solution with a higher solute concentration than the cell's cytoplasm). Water then moves out of the cell, specifically from the vacuole, by osmosis. Here's a breakdown:
- The Role of Vacuoles: Vacuoles are organelles within plant cells that are primarily responsible for maintaining turgor pressure, which is the pressure of the cell contents against the cell wall. They also store water, nutrients, and waste products.
- Water Loss: In a hypertonic environment, water flows out of the vacuole and the cytoplasm.
- Vacuole Shrinkage: As water leaves the vacuole, it decreases in size, hence the diameter of the vacuoles shrinks.
- Cytoplasmic Separation: The cytoplasm then shrinks and pulls away from the cell wall. This separation is plasmolysis.
- Loss of Turgor: The cell loses its turgidity, leading to wilting or a flaccid state, because turgidity is controlled by vacuoles, which govern the quantity of water inside the cell.
Consequences of Vacuole Shrinkage During Plasmolysis
The shrinking of the vacuole is not just a physical change; it has significant consequences for the plant cell:
- Wilting: As the vacuoles lose water and the cells lose turgor pressure, the plant wilts.
- Cellular Function Impairment: Plasmolysis can disrupt normal cellular functions, as the cytoplasm is no longer in close contact with the cell wall, potentially affecting nutrient and waste exchange.
Example: Plasmolysis in a Leaf Cell
Imagine a leaf cell in a plant placed in a salty environment.
- The salt concentration outside the cell is higher than inside.
- Water from the vacuole within the leaf cell moves out into the salty environment via osmosis.
- The vacuole shrinks.
- The cytoplasm of the leaf cell pulls away from the cell wall, which results in the plasmolysis of the leaf cell.
- The leaf begins to wilt.
