Question

If a cell with O.P. 10 bars and T.P. 4 bars is connected to cells B, C, and D having O.P. and T.P. 4 and 4, 10 and 5 and 7 and 3 bars respectively, the flow of water will be
(a) C to A, B, and D
(b) B to A, C, and D
(c) A to D, B, and C
(d) A to B, C, and D

Answer 1

Concepts such as osmotic pressure O.P., turgor pressure T.P. and diffusion pressure deficit DPD are crucial in understanding the water movement inside the plant cells. There is a relation between all these three values and the difference in the values of DPD is responsible for water movement.

Complete Answer:
Osmotic Pressure : It is defined as the amount of pressure that needs to be applied to a solution to present the flow of solvent (water) from the pure solvent through a semipermeable membrane. The higher the amount of solute in a solution, the higher will be its osmotic pressure. The solvent moves from a solution of low osmotic pressure (dilute solution) to a solution of high osmotic pressure (concentrated solution).
Turgor Pressure : It is defined as the amount of pressure applied to the walls of the cell due to the amount of solvent present in it. The higher the solvent i.e. water present in a cell, the more will be the turgor pressure of that cell. Water moves from a cell with high turgor pressure (dilute solution) to low turgor pressure (concentrated solution).
Diffusion Pressure Deficit : It is defined as the amount by which the diffusion pressure of a solution is less than its pure solvent. High DPD implies the tendency for diffusion for that solution is much much lesser than the pure solvent. Water moves from low DPD (dilute solution) to high DPD (concentrated solution).
DPD = OP - TP
For A, DPD = 10 - 4 = 6 bars
For B, DPD = 4 - 4 = 0 bars
For C, DPD = 10 - 5 = 5 bars
For D, DPD = 7 - 3 = 4 bars
As we know water flows from low DPD to high DPD, water will flow from B to all the other cells as it has the lowest DPD.
So, the correct option is ‘B to A, C, and D’.

Note:
- DPD of a turgid cell is 0.
- TP of a flaccid and plasmolyzed cell is 0.
- OP of a pure solvent is 0 as it has no solute present in it.