In a fully turgid cell, what is equal to zero?
(a) Turgor pressure
(b) Osmotic pressure
(c) Wall pressure
(d) Diffusion pressure deficit

Options

A. Turgor pressure
B. Osmotic pressure
C. Wall pressure
D. Diffusion pressure deficit

Answer

To solve the question "In a fully turgid cell, what is equal to zero?", we need to analyze the concepts of turgor pressure, osmotic pressure, wall pressure, and diffusion pressure deficit (DPD).

### Step-by-Step Solution:

1. **Understanding Turgidity**:
- A fully turgid cell is one that has absorbed water to the point where the internal pressure (turgor pressure) pushes against the cell wall. This occurs when the cell is placed in a hypotonic solution, where the external water concentration is higher than that inside the cell.

**Hint**: Recall that turgidity is related to the pressure exerted by water inside the cell.

2. **Osmotic Pressure**:
- Osmotic pressure is the pressure required to prevent the flow of water into the cell. In a turgid cell, the osmotic pressure is balanced by the turgor pressure exerted against the cell wall.

**Hint**: Think about how water moves in and out of cells based on concentration gradients.

3. **Turgor Pressure**:
- Turgor pressure is the pressure exerted by the fluid (water) inside the vacuole against the cell wall. In a fully turgid cell, this pressure is at its maximum.

**Hint**: Consider the relationship between turgor pressure and osmotic pressure.

4. **Wall Pressure**:
- Wall pressure is the pressure exerted by the cell wall against the turgor pressure. In a fully turgid cell, wall pressure is equal to turgor pressure.

**Hint**: Remember that wall pressure and turgor pressure are closely related in a turgid cell.

5. **Diffusion Pressure Deficit (DPD)**:
- DPD is the difference between the osmotic pressure of the solution and the actual pressure in the cell. In a fully turgid cell, the osmotic pressure equals the turgor pressure, meaning that there is no deficit in pressure driving water movement.

**Hint**: DPD is a measure of the potential for water movement; think about what happens when a cell is fully turgid.

6. **Conclusion**:
- In a fully turgid cell, the diffusion pressure deficit (DPD) is equal to zero because there is no net movement of water into or out of the cell. Therefore, the correct answer is (d) Diffusion pressure deficit.

### Final Answer:
(d) Diffusion pressure deficit