Question

Cell A and cell B are adjacent plant cells. In cell A, ${\psi }_S=-20$ bars and ${\psi }_P=8$ bars. In cell 'B', ${\psi }_S=-12$ bars and ${\psi }_P=2$. Then,

• A. Water moves from cell B to cell A.
• B. Equal amount of water is simultaneously exchanged between cell A and cell B.
• C. Water moves from cell A to cell B.
• D. There is no movement of water between cell A and cell B.

Answer 1

The correct option is A Water moves from cell B to cell A.

For cell A, Ψs = -20 bars and Ψp = 8 bars

Water potential Ψw = Ψs + Ψp = -20 + 8 = -12 bars

For cell B, Ψs = -12 bars and Ψp = 2 bars

Water potential Ψw = Ψs + Ψp = -12 + 2 = -10 bars

Ψw for cell A < Ψw for cell B

Since water moves from a region of higher water potential to a region of low water potential, therefore, water will move from cell B to cell A.

(Note: The more negative is the value, the lower is the water potential.)

So, the correct answer is A.