Two cells A and B are contiguous. Cell A has osmotic pressure 10 atm, turgor pressure 7 atm and diffusion…

38 2007 AIPMT-PRE Transport in PlantsPlant-Water Relations Medium
Two cells A and B are contiguous. Cell A has osmotic pressure 10 atm, turgor pressure 7 atm and diffusion pressure deficit 3 atm. Cell B has osmotic pressure 8 atm, turgor pressure 3 atm and diffusion pressure deficit 5 atm. The result will be
A no movement of water
B equilibrium between the two
C movement of water from cell A to B
D movement of water from cell B to A

Detailed Solution

Diffusion pressure deficit (DPD) = osmotic pressure (OP) - turgor pressure (TP).
For cell A: DPD = 10 - 7 = 3 atm.
For cell B: DPD = 8 - 3 = 5 atm.
DPD is the suction pressure of a cell; it measures the ability of the cell to absorb water.
Water always moves from a cell with lower DPD to a cell with higher DPD (i.e. from higher water potential to lower water potential), whatever the osmotic pressures may be.
Cell B has the higher DPD (5 atm) and cell A has the lower DPD (3 atm).
So water will move from cell A to cell B, even though cell A has the higher osmotic pressure.

Transport in Plants in past papers

41 questions from this chapter have appeared across 18 exam years.

Keep going

Practise Transport in Plants All 41 questions This chapter in 2007 AIPMT-PRE