For a plasmolysed cell, which equation is correct ?

Options

A. DPD = OP + TP
B. DPD = - TP
C. DPD = OP
D. DPD = OP - TP

Answer

To solve the question regarding the correct equation for a plasmolysed cell, we need to understand the concepts of osmotic pressure (OP), turgor pressure (TP), and diffusion pressure deficit (DPD).

### Step-by-Step Solution:

1. **Understand the Definitions**:
- **Osmotic Pressure (OP)**: This is the pressure required to prevent the movement of water from a pure water solution to a concentrated solution.
- **Turgor Pressure (TP)**: This is the pressure exerted by the cell contents (protoplasm) against the cell wall.
- **Diffusion Pressure Deficit (DPD)**: This is calculated as the difference between osmotic pressure and turgor pressure. The formula is:
\[ DPD = OP - TP \]

2. **Analyze a Plasmolysed Cell**:
- In a plasmolysed cell, the cell contents shrink away from the cell wall due to loss of water. This means that the turgor pressure (TP) will be very low, approaching zero, because the protoplasm is not exerting pressure against the cell wall.

3. **Calculate DPD for a Plasmolysed Cell**:
- Since in a plasmolysed cell, TP is nearly zero, we can substitute this into the DPD equation:
\[ DPD = OP - TP \implies DPD = OP - 0 \implies DPD = OP \]

4. **Conclusion**:
- Therefore, for a plasmolysed cell, the correct equation is:
\[ DPD = OP \]

### Final Answer:
The correct equation for a plasmolysed cell is:
\[ DPD = OP \]