Changes Due to Water Movement in Plant Tissue Bathed in Hypotonic and Hypertonic Solutions
- When plant tissues are placed in different solutions, water flows in or out of their cells.
- This causes dramatic changes in their texture and structure.
Hypotonic Solutions: Water Moves Into Cells
Hypotonic
A solution with a lower solute concentration compared to another solution.
- When plant tissue is placed in a hypotonic solution, water moves into the cells by osmosis.
- This causes the cells to swell and become turgid.
Turgid
Turgid refers to a plant cell that is swollen with water, causing the cell membrane to press tightly against the cell wall.
Why Does This Happen?
- The water potential of the hypotonic solution is higher than that of the cell's cytoplasm.
- Water moves from the solution into the cell to equalize the water potential.
Effects on Plant Tissue
- Increased Mass and Length: The tissue gains water, increasing its mass and sometimes its length.
- Firmness: The cells become turgid, making the tissue firm and rigid.
- Turgidity is essential for plants to maintain their structure.
- It helps non-woody plants stand upright and keeps leaves firm.
Hypertonic Solutions: Water Moves Out of Cells
Hypertonic
A solution with a higher solute concentration compared to another solution.
- When plant tissue is placed in a hypertonic solution, water moves out of the cells by osmosis.
- This causes the cells to shrink and become plasmolysed.
Plasmolysis
Plasmolysis is the process where the cell membrane pulls away from the cell wall due to water loss.
Why Does This Happen?
- The water potential of the hypertonic solution is lower than that of the cell's cytoplasm.
- Water moves from the cell into the solution to equalize the water potential.
Effects on Plant Tissue
- Decreased Mass and Length: The tissue loses water, reducing its mass and sometimes its length.
- Softness and Wilting: The cells become flaccid, making the tissue soft and limp.
Don't confuse turgidwith plasmolysed. Turgid cells are swollen with water, while plasmolysed cells have lost water and shrunk.
Isotonic Solutions: No Net Water Movement
Isotonic
Two solutions with equal solute concentrations, resulting in no net movement of water.
- When plant tissue is placed in an isotonic solution, there is no net movement of water.
- The tissue remains unchanged in mass and firmness.
Think of isotonic solutions as a balanced seesaw. Water moves in and out of the cells at equal rates, so there's no overall change.
Measuring Changes in Plant Tissue
- To study osmosis, you can measure changes in the mass and length of plant tissue before and after placing it in different solutions.
- Here's how:
