Which one is correct ?

Options

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

Answer

To determine which equation is correct regarding water potential in plants, we will analyze the components that contribute to water potential and how they interact.

### Step-by-Step Solution:

1. **Understanding Water Potential (Ψ)**:
- Water potential (Ψ) is a measure of the potential energy of water in a system and is crucial for understanding water movement in plants. It is influenced by solute concentration and pressure.

2. **Components of Water Potential**:
- Water potential is comprised of three main components:
- **Solute Potential (Ψs)**: This is the potential of water to move based on solute concentration. Pure water has a solute potential of 0, and as solute concentration increases, the solute potential becomes more negative.
- **Pressure Potential (Ψp)**: This is the physical pressure exerted on water in a plant cell. When pressure increases, the pressure potential increases, which contributes positively to water potential.
- **Matrix Potential (Ψm)**: This refers to the potential energy of water bound to the plant matrix (like cell walls). It is generally negative and can be ignored in well-watered systems.

3. **Water Potential Equation**:
- The general equation for water potential can be expressed as:
\[ Ψ = Ψs + Ψp + Ψm \]
- In most plant systems, especially when well-watered, the matrix potential (Ψm) can be ignored, simplifying the equation to:
\[ Ψ = Ψs + Ψp \]

4. **Analyzing the Options**:
- Based on the explanation provided, we can conclude that the correct equation for water potential in plants is:
\[ Ψ = Ψs + Ψp \]
- The option that reflects this equation is option number 3.

5. **Conclusion**:
- Therefore, the correct answer to the question "Which one is correct?" is option number 3.