During the transport of water, the value of which of the following is always negative ?

Options

A. water potential
B. Solute potential
C. Pressure potential
D. Both (B) and (C)

Answer

To solve the question regarding which value is always negative during the transport of water, we will analyze the three options provided: water potential, solute potential, and pressure potential.

### Step-by-Step Solution:

1. **Understanding Water Potential (Ψw)**:
- Water potential is a measure of the potential energy of water in a system and is represented by Ψw.
- It is influenced by solute potential and pressure potential. Water potential is generally considered to be positive or zero in pure water.

2. **Understanding Solute Potential (Ψs)**:
- Solute potential, also known as osmotic potential, is the potential of water to move into a solution due to the presence of solute. It is represented by Ψs.
- When solute is added to water, it causes a decrease in water potential.
- Importantly, solute potential is always negative or zero because it reflects the tendency of water to move into the solution (the more solute present, the lower the solute potential).

3. **Understanding Pressure Potential (Ψp)**:
- Pressure potential is the physical pressure exerted by the cell wall against the cell contents. It is represented by Ψp.
- This value can be positive (when the cell is turgid) or zero (when the cell is flaccid). It is not always negative.

4. **Conclusion**:
- Among the three values, only solute potential (Ψs) is always negative.
- Therefore, the correct answer to the question is **solute potential**.

### Final Answer:
The value that is always negative during the transport of water is **solute potential (Ψs)**.

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