Skip to content
Myclass24

Name the two factors on which water potential depends? Also give its relationship with them.

GeneralClass 12AllAnswered 27 Mar 2026
Answer

Water potential (Ψ<sub>w</sub>) depends on two components:

Factor

Symbol

Nature

Effect on Ψ<sub>w</sub>

Solute Potential (Osmotic Potential)

Ψ<sub>s</sub>

Always negative or zero

Decreases Ψ<sub>w</sub>

Pressure Potential (Turgor Pressure)

Ψ<sub>p</sub>

Can be positive or negative

Increases (if +ve) or decreases (if -ve) Ψ<sub>w</sub>

Relationship:

Ψ<sub>w</sub> = Ψ<sub>s</sub> + Ψ<sub>p</sub>

Detailed Explanation:

  1. Solute Potential (Ψ<sub>s</sub>):
    • Effect of dissolved solutes
    • Always ≤ 0 (negative or zero)
    • Pure water: Ψ<sub>s</sub> = 0
    • More solutes → more negative Ψ<sub>s</sub>
  2. Pressure Potential (Ψ<sub>p</sub>):
    • Physical pressure on water
    • Positive in turgid cells
    • Negative in xylem (tension)
    • Zero at atmospheric pressure

Special Cases:

  • Pure water at atmospheric pressure: Ψ<sub>w</sub> = 0 + 0 = 0 (reference point)
  • Fully turgid cell: Ψ<sub>w</sub> = 0 (when Ψ<sub>p</sub> = |Ψ<sub>s</sub>|)
  • Plasmolyzed cell: Ψ<sub>p</sub> = 0, so Ψ<sub>w</sub> = Ψ<sub>s</sub> (negative)

Suggested Q&A

General · Class 12