The `psi_(W)` of imbibants is

Options

A. highly negative
B. highly positive
C. zero
D. always positive

Answer

### Step-by-Step Solution:

1. **Understanding Imbibition**:
- Imbibition is the process of absorption of water by solid particles of an absorbent without forming a solution. It is crucial in the context of seed germination and plant growth.

2. **Defining Key Terms**:
- **Imbibent**: The solid material that absorbs water (e.g., seeds, dry wood).
- **Imbibate**: The fluid that is absorbed, which is typically water.

3. **Water Potential (Ψ)**:
- Water potential (Ψ) is a measure of the potential energy in water, influencing the movement of water in plants. It is composed of two main components: matric potential and pressure potential (turgor pressure).

4. **Components of Water Potential**:
- The water potential of an imbibent can be expressed as:
\[ Ψ = Ψ_m + Ψ_p \]
where:
- \(Ψ_m\) = Matric potential (related to the attraction of water to the solid surface).
- \(Ψ_p\) = Pressure potential (also known as turgor pressure, which is the pressure exerted by the fluid inside the cell against the cell wall).

5. **Condition of Imbibition**:
- In the case of imbibition, if the imbibent is confined and does not exert turgor pressure, the equation simplifies to:
\[ Ψ = Ψ_m \]
- This indicates that the water potential is primarily determined by the matric potential.

6. **Water Potential Values**:
- Water potential values can be negative. Pure water has a water potential of zero (Ψ = 0). Therefore, the water potential of an imbibent is typically highly negative due to the strong attraction of water to the solid particles.

7. **Conclusion**:
- The water potential of imbibants (imbibents) is highly negative, reflecting the strong affinity of the solid material for water.