Solute and Pressure Potential Changes When Plant Cells Are Bathed in Different Solutions
- Recall the principles of water potential: water moves from areas of higher potential energy to areas of lower potential energy.
- This movement is driven by two key factors: solute potential and pressure potential.
- When plant tissue interacts with different solutions, these factors determine whether water enters or exits the cells and the effects can be dramatic.
Definition
Solute potential
Solute potential ($\psi_s$) measures how solutes affect water's potential energy.
Definition
Pressure potential
Pressure potential ($\psi_p$) reflects the physical pressure exerted on water.
Plant Tissue in Hypotonic Solutions
What Is a Hypotonic Solution?
- When plant tissue is placed in a hypotonic solution, water moves into the cells by osmosis.
Definition
Hypotonic
A solution with a lower solute concentration compared to another solution.
Turgor pressure is essential for maintaining the rigidity of plant tissues, helping them stand upright.
What Happens to Plant Cells?
- Water movement: Water enters the cell because the water potential of the solution is higher than the water potential inside the cell.
- Turgor pressure: As water fills the central vacuole, pressure builds inside the cell. This is called turgor pressure, and it pushes the plasma membrane tightly against the cell wall.
- Result: The cell becomes turgid and firm. Turgor pressure supports plant structure and keeps stems and leaves upright.
Equilibrium in Hypotonic Solutions
- Water continues to enter the cell until the water potential inside the cell equals that of the surrounding solution.
- At this point, there is no net movement of water.
Plants thrive in hypotonic environments, as turgor pressure is essential for growth and structural support.
