The lowest water potentials in the xylem are in the

Options

A. root hairs
B. vascular cylinders of roots
C. tracheids of the stem
D. transpiring leaves .

Answer

**Step-by-Step Solution:**

1. **Understanding Water Potential**:
- Water potential (Ψ) is a measure of the potential energy of water in a system and is influenced by solute concentration and pressure. Pure water has a maximum water potential of zero.

2. **Effect of Solutes on Water Potential**:
- The addition of solutes to water decreases its water potential. This is because solutes attract water molecules, effectively reducing the amount of free water available.

3. **Analyzing the Options**:
- The question provides four options: root hairs, vascular slenderness of roots, tracheids of the stem, and transpiring leaves. We need to evaluate which of these has the lowest water potential.

4. **Evaluating Each Option**:
- **Root Hairs**: These structures are in direct contact with soil water, thus they have a relatively high water potential.
- **Vascular Slenderness of Roots**: Similar to root hairs, these are also in contact with water and do not lose water, indicating a higher water potential.
- **Tracheids of the Stem**: These are involved in water transport but do not lose water directly, hence they also maintain a higher water potential.
- **Transpiring Leaves**: Leaves lose water continuously through transpiration. This loss of water increases the solute concentration in the xylem, leading to a decrease in water potential.

5. **Conclusion**:
- Since transpiring leaves continuously lose water, they have the lowest water potential among the options provided. Therefore, the correct answer is **transpiring leaves**.

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