Select an incorrect statement for pressure potential

Options

A. If a pressure greater than atmospheric pressure is applied to pure water or a solution, its water potential increases.
B. n plants negative pressure potential or tension in the water column in the xylem plays a major role in watertransport up a stem.
C. Pressure potential is usually positive.
D. When water enters a plant cell its pressure potential decreases

Answer

To solve the question of selecting an incorrect statement regarding pressure potential, let's analyze the statements one by one based on the information provided in the video transcript.

### Step-by-Step Solution:

1. **Understanding Pressure Potential**:
- Pressure potential is a component of water potential. Water potential is the measure of the potential energy of water in a system, which influences the movement of water between different systems.

2. **Analyzing the Statements**:
- **Statement 1**: "If a pressure greater than atmospheric pressure is applied to pure water or a solution, its water potential increases."
- This statement is **correct** because applying pressure increases the water potential.

- **Statement 2**: "In plants, negative pressure potential or tension in the water column in the xylem plays a major role in water transport up a stem."
- This statement is also **correct**. Negative pressure potential indeed helps in the upward movement of water through the xylem.

- **Statement 3**: "Pressure potential is usually positive."
- This statement is **correct** as well. In most cases, pressure potential is positive in plant cells when they are turgid.

- **Statement 4**: "When the water enters the plant cell, its pressure potential increases."
- This statement is also **correct**. When water enters a plant cell, it causes the cell to swell, increasing the pressure potential.

3. **Identifying the Incorrect Statement**:
- After analyzing all the statements, it appears that all the statements provided are actually correct based on the definitions and roles of pressure potential in plants. However, the question asks for an incorrect statement. If we assume that the question is looking for a misunderstanding or a common misconception, the statement that could be considered incorrect might be one that is not commonly accepted or is misinterpreted in a different context.

### Conclusion:
- All statements provided are correct based on the understanding of pressure potential. If forced to select an incorrect statement, one would need to clarify the context or look for a statement that is commonly misinterpreted.