Presence of hair on the leaf surface

Options

A. Reduces transpiration
B. Increases transpiration
C. Helps in repid exchange of gases
D. Pervents guttation

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the effect of hair on the leaf surface. We need to analyze how these hairs (trichomes) influence transpiration and other processes.

2. **Identifying the Options**:
- a. Reduce transpiration
- b. Increase transpiration
- c. Helps in rapid exchange of gases
- d. Prevents curtation

3. **Analyzing the Role of Leaf Hairs**:
- Leaf hairs, or trichomes, are small outgrowths on the epidermis of leaves.
- They can create a microenvironment that reduces air movement around the leaf surface.

4. **Effect on Transpiration**:
- By reducing air movement, leaf hairs can decrease the rate of transpiration. This is because less wind means less evaporation of water from the leaf surface.
- Therefore, the presence of hairs acts as a windbreak, helping to retain moisture.

5. **Evaluating Other Options**:
- **Option b (Increase transpiration)**: This is incorrect since the hairs reduce air movement, which in turn reduces transpiration.
- **Option c (Helps in rapid exchange of gases)**: While some trichomes may aid in gas exchange, their primary role is not to facilitate rapid gas exchange.
- **Option d (Prevents curtation)**: This option is not directly related to the function of leaf hairs.

6. **Conclusion**: Based on the analysis, the presence of hair on the leaf surface primarily serves to reduce transpiration.

### Final Answer:
The correct answer is **a. Reduce transpiration**.

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