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Plant-Water Relations
Concepts tested here
- Diffusion pressure deficit
All Questions
2007 AIPMT-PRE 1 question
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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 beDiffusion 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.