Question

For a plasmolysed cell which of the following equations is correct?
A) DPD = OP + TP
B) DPD = - TP
C) DPD = OP
D) DPD = OP – TP

Answer 1

Hint: The plant cells/tissues’ behavior for the movement of water depends on the surrounding solution. Plasmolysis occurs when water exits the cell membrane of a plant cell and shrinks away from its cell wall. This occurs when the cell is placed in a hypertonic solution to the protoplasm.

Complete answer:
DPD means Diffusion pressure deficit, OP means osmotic pressure, and TP means turgor pressure.
DPD calculated as DPD= Osmotic Pressure (OP) - Turgor Pressure (TP)
When a cell is placed in a hypotonic solution, water actually flows out of the cell into the surrounding solution. This causes the protoplast to shrink away from the cell wall. This condition is known as plasmolysis. When water moves out, it is the first loss from the cytoplasm and then from the vacuole. The stage of plasmolysis, in which the first sign of shrinkage of protoplast from the cell wall becomes detectable is called incipient plasmolysis. At incipient plasmolysis. The protoplast does not exert pressure against the wall, nor is it separated from the wall. Consequently, turgor pressure is zero. Thus DPD is equal to the OP.
A) DPD = OP + TP – it is the general formula. So it is the wrong answer
B) DPD = - TP it is also a wrong option.
C) DPD = OP – correct option.
D) DPD = OP – TP also an incorrect option.

The right answer is option ( C ) that is “DPD = OP”.

Note:
• If the outer solution balances the osmotic pressure of the cytoplasm, it is called Isotonic.
• If the outer solution is more dilute than the cytoplasm, it is called Hypotonic.
• If the outside solution is more concentrated than the cytoplasm, it is called Hypertonic