Question

In flaccid cell
A. DPD = WP
B. DPD = OP
C. DPD = 0
D. DPD = OP-TP

Answer 1

Hint: At the point when a plant cell is flaccid, turgor pressure gets zero and the diffusion pressure deficit (DPD) is equal to the osmotic potential (OP).

Complete answer:
The water has the tendency to move from an area of lower diffusion pressure deficit (DPD) to an area of higher DPD. The DPD is calculated as-
Diffusion pressure deficit = osmotic pressure – turgor pressure
DPD = OP – TP
When a plant cell is a flaccid cell i.e. TP = 0
DPD = OP – 0
DPD = OP

Additional information:
- Turgor pressure: It is the pressure applied by the tonoplast against the cell wall which is zero in the flaccid cell and maximum in the turgid cell. When a plant cell is placed in an isotonic solution that has the same concentrations of solute in the inside and outside of a plant cell, the cell becomes flaccid. The cell membrane has no turgor pressure means it is not pressed against the cell wall tightly.
- Osmotic pressure: Osmotic pressure is the excess pressure which is applied in the solution to separate the solution from its pure solvent by a semipermeable membrane. It depends on the number of solute molecules but not on the size of molecules.

So, the correct answer is ‘DPD = OP’

Note:
- In hypertonic conditions, the water moves out of the cell to the higher solute concentration region, and the cell becomes plasmolyzed.
- In hypotonic conditions, the water easily moves inside the cell due to lower solute concentration of the solution and the cell becomes turgid.
- In the case of RBCs, the isotonic condition is ideal to maintain the shape of the cells. In an animal cell, the absence of a cell wall may cause the cell to burst under pressure.