Correct expression of the following is

Options

A. `Psi_(w) =Psi_(s)-Psi_(p)`
B. `Psi_(s) =Psi_(w) + Psi_(p)`
C. `Psi_(w) =Psi_(s)+Psi_(p)`
D. `Psi_(p) = Psi_(w)+Psi_(s)`

Answer

To solve the question regarding the correct expression involving water potential (ψw), solute potential (ψs), and pressure potential (ψp), we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Variables**:
- **ψw (Water Potential)**: This is the potential energy of water in a system compared to pure water, and it determines the direction of water movement.
- **ψs (Solute Potential)**: This is the potential of a solution to take in water, which is influenced by the concentration of solutes.
- **ψp (Pressure Potential)**: This is the physical pressure exerted on the solution, which can affect the water potential.

2. **Know the Relationship**:
- The relationship between these potentials is defined in plant physiology. The water potential is the sum of the solute potential and the pressure potential.

3. **Write the Correct Expression**:
- The correct expression that relates these three potentials is:
\[ ψw = ψs + ψp \]

4. **Identify the Correct Option**:
- Based on the options provided:
- Option 1: ψw = ψs - ψp
- Option 2: ψs = ψw + ψp
- Option 3: ψw = ψs + ψp (This is the correct expression)
- Option 4: ψp = ψw + ψs
- The correct answer is **Option 3: ψw = ψs + ψp**.

### Final Answer:
The correct expression is **Option 3: ψw = ψs + ψp**.