Water potentialis generally most negative in

Options

A. the soil solution
B. mesophyll cell walls
C. xylem sap of roots
D. xylem sap of leaves

Answer

**Step-by-Step Solution:**

1. **Understanding Water Potential**: Water potential is a measure of the potential energy in water, which influences the movement of water in plants. It is affected by solute concentration and pressure.

2. **Identifying the Options**: The question provides four options:
- Option 1: Soil solution
- Option 2: Mesophyll cell walls
- Option 3: Xylem sap of roots
- Option 4: Xylem sap of leaves

3. **Analyzing Water Movement**: Water moves from areas of higher water potential to areas of lower water potential. In plants, this movement typically occurs from the soil (high water potential) through the roots, stems, and leaves, and finally into the atmosphere (low water potential).

4. **Evaluating Each Option**:
- **Soil Solution**: Generally has a higher water potential (less negative) compared to other parts of the plant.
- **Xylem Sap of Roots**: Also has a relatively higher water potential compared to the leaves.
- **Xylem Sap of Leaves**: Has a lower water potential than the roots but is not the lowest.
- **Mesophyll Cell Walls**: Water evaporates from the mesophyll cells into the air spaces of the leaf. When the surrounding air has low water vapor, the water potential in the mesophyll cell walls becomes very negative due to the loss of water vapor.

5. **Conclusion**: The water potential is generally most negative in the mesophyll cell walls because this is where water is lost to the atmosphere, especially when the air is dry.

6. **Final Answer**: Therefore, the correct answer is **Option 2: Mesophyll cell walls**.

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