Water potential (ψ) can be thought of as the tendency for water to move from one place to another. In plants, it is made up mainly of solute potential and pressure potential. Hypothetical plant cells A and B are adjacent to each other. The solute potential (ψS) of cell A is −0.35 MPa, and its pressure potential (ψP) is +0.15 MPa. The solute potential (ψS) of cell B is −0.30 MPa, and its pressure potential (ψP) is +0.05 MPa. In which direction will net water movement occur?

Question

Quizplus · Accepted Answer

Water potential (ψ) is calculated as the sum of solute potential (ψS) and pressure potential (ψP). For cell A, ψ = ψS + ψP = -0.35 + 0.15 = -0.20 MPa. For cell B, ψ = ψS + ψP = -0.30 + 0.05 = -0.25 MPa. Water moves from a region of higher water potential to a region of lower water potential, so it will move from cell A (ψ = -0.20 MPa) to cell B (ψ = -0.25 MPa).

Water Potential (ψ) Can Be Thought of as the Tendency