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How solute potential, water potential and pressure potential of a cell (plant) vary when kept in hypotonic solution?

GeneralClass 12AllAnswered 27 Mar 2026
Answer

When a plant cell is placed in a hypotonic solution (solution with higher water potential than the cell):

Sequential Changes:

Stage

Water Movement

Ψ<sub>p</sub>

Ψ<sub>s</sub>

Ψ<sub>w</sub>

Cell Condition

Initial

None

Low/zero

Negative (constant)

Negative

Flaccid

Intermediate

Water enters (osmosis)

Increasing (positive)

Slightly less negative (dilution)

Increasing (less negative)

Swelling

Final (Equilibrium)

Stopped

Maximum (= |Ψ<sub>s</sub>|)

Most negative value

Zero

Fully turgid

Detailed Explanation:

  1. Water Potential (Ψ<sub>w</sub>): Increases from negative to zero when equilibrium is reached
  2. Pressure Potential (Ψ<sub>p</sub>): Increases progressively as turgor pressure builds up, reaching maximum when Ψ<sub>w</sub> = 0
  3. Solute Potential (Ψ<sub>s</sub>): Becomes slightly less negative due to:
    • Dilution of cell sap (minor effect)
    • Remains relatively constant in large vacuoles

Critical Point: Water entry stops when: Ψ<sub>p</sub> = |Ψ<sub>s</sub>|

This makes Ψ<sub>w</sub> = 0, creating dynamic equilibrium with the hypotonic solution.

Biological Significance: This mechanism prevents plant cells from bursting (unlike animal cells, which lack rigid cell walls).

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General · Class 12