A plant cell loses water and the contents shrink away from the wall.
Explanation
Plasmolysis is a specific physiological phenomenon observed in plant cells, bacteria, and fungi, which possess a rigid cell wall. It refers to the contraction or shrinkage of the protoplast of a plant cell from its cell wall.Mechanism of Plasmolysis:
- Condition: It occurs when a living plant cell is placed in a hypertonic solution (a solution with a higher solute concentration than the cell sap).
- Process: Water moves out of the cell across the semi-permeable plasma membrane through the process of exosmosis to balance the concentration gradient.
- Result: As water is lost, turgor pressure decreases. Eventually, the protoplasm (cytoplasm and nucleus) shrinks and pulls away from the rigid cell wall. This state is called plasmolysis.
Analysis of Other Options:
- A plant cell absorbs water and swells.: Absorption of water leading to swelling is known as deplasmolysis or the development of turgidity, which occurs in a hypotonic solution.
- The cell wall ruptures due to high pressure.: The cell wall is rigid and provides structural support, preventing the cell from rupturing even under high internal pressure (turgor pressure). Rupturing is more characteristic of animal cells (lysis) in hypotonic conditions.
- The nucleus divides into two.: The division of the nucleus into two is termed karyokinesis, a stage in cell division.
Key Takeaway: Plasmolysis is the shrinkage of the protoplast from the cell wall caused by exosmosis when a plant cell is exposed to a hypertonic environment.