Choose the option with correct expression.

Options

A. `psi_w=psi_s-psi_p`
B. `psi_s=psi_w+psi_p`
C. `psi_w=psi_s+psi_p`
D. `psi_w=psi_p-psi_s`

Answer

To solve the question regarding the correct expression for water potential, we can break down the solution into the following steps:

### Step-by-Step Solution:

1. **Understanding Water Potential**:
Water potential (Ψ) is a measure of the potential energy in water, which determines the direction of water movement. It is represented by the symbol Ψ and is influenced by solute potential (Ψs) and pressure potential (Ψp).

2. **Components of Water Potential**:
The water potential can be expressed using the formula:
\[ Ψ = Ψs + Ψp \]
- **Ψs (Solute Potential)**: This is the potential energy of water due to the presence of solutes. It is usually negative because the addition of solute lowers the water potential.
- **Ψp (Pressure Potential)**: This is the physical pressure exerted on the water in a system. It can be positive or zero.

3. **Direction of Water Movement**:
Water moves from areas of higher water potential to areas of lower water potential. This movement is influenced by both solute concentration and pressure.

4. **Identifying the Correct Expression**:
In the context of the question, we need to identify which option correctly represents the relationship between water potential, solute potential, and pressure potential.

5. **Evaluating the Options**:
- The options provided likely include various expressions for water potential. We need to check which option correctly follows the formula Ψ = Ψs + Ψp and adheres to the principles of water potential (e.g., Ψ cannot be negative if it is purely pressure potential).

6. **Selecting the Correct Option**:
Based on the analysis, the third option is identified as correct because it aligns with the principles of water potential and does not violate the rules regarding solute and pressure potentials.

### Final Answer:
The correct expression for water potential is represented in the third option.

---