Which one is correct ?

Options

A. `Psi_(m)=Psi_(p)+Psi_(s) +Psi_(w)`
B. `Psi_(w)=Psi_(p)+Psi_(s)+Psi_(m)`
C. `Psi_(p)=Psi_(w)+Psi_(m)+Psi_(s)`
D. all are correct

Answer

To solve the question regarding which statement is correct about the different potentials in plants, we will analyze the definitions and relationships between the various potentials mentioned: matric potential, water potential, solute potential, and pressure potential.

### Step-by-Step Solution:

1. **Understanding Matric Potential (Ψm)**:
- Matric potential refers to the potential energy of water in relation to its adhesion to solid surfaces, such as soil particles and plant cell walls. It is a measure of how much water is held in the soil or plant material due to these adhesive forces.
- **Hint**: Remember that matric potential is influenced by the binding of water to materials.

2. **Understanding Water Potential (Ψw)**:
- Water potential is the overall potential energy of water in a system, which determines the direction of water movement. It is influenced by both solute potential and pressure potential.
- **Hint**: Water potential is a measure of the kinetic energy of water molecules.

3. **Understanding Solute Potential (Ψs)**:
- Solute potential is the component of water potential that is affected by the concentration of solutes in the solution. It is always negative or zero, as the addition of solutes lowers the water potential compared to pure water.
- **Hint**: More solute means a more negative solute potential.

4. **Understanding Pressure Potential (Ψp)**:
- Pressure potential is the physical pressure exerted on or by a solution. When pressure is applied to a solution, it increases the water potential. In turgid cells, the pressure potential is positive due to turgor pressure.
- **Hint**: Pressure potential increases water potential when external pressure is applied.

5. **Combining the Potentials**:
- The relationship between these potentials can be summarized in the equation:
\[ \Psi_w = \Psi_s + \Psi_p + \Psi_m \]
- This equation indicates that water potential is the sum of solute potential, pressure potential, and matric potential.

6. **Identifying the Correct Statement**:
- Based on the definitions and relationships, the correct statement is that water potential is equal to the sum of solute potential, matric potential, and pressure potential.
- **Final Answer**: The correct option is that water potential (Ψw) is equal to solute potential (Ψs) plus matric potential (Ψm) plus pressure potential (Ψp).