Transpiration is least in
(a) Good soil moisture
(b) High wind velocity
(c) Dry environment
(d) High atmospheric humidity

Options

A. Good soil moisture
B. High wind velocity
C. Dry environment
D. High atmospheric humidity.

Answer

To determine in which condition transpiration is least, we need to analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Transpiration**:
- Transpiration is the process by which water vapor is lost from the aerial parts of the plant, primarily through small openings called stomata.

2. **Analyzing Each Option**:
- **(a) Good soil moisture**:
- When soil moisture is good, plants have adequate water supply, which can lead to increased transpiration as there is enough water for the plant to lose.
- **(b) High wind velocity**:
- High wind velocity can actually increase the rate of transpiration because it helps to remove water vapor from around the stomata, maintaining a gradient that encourages more water loss.
- **(c) Dry environment**:
- In a dry environment, the air has low humidity. This creates a strong vapor pressure gradient between the inside of the leaf and the outside air, leading to increased transpiration.
- **(d) High atmospheric humidity**:
- High atmospheric humidity means that the air is saturated with water vapor. This reduces the vapor pressure gradient between the inside of the leaf and the outside environment, resulting in decreased transpiration.

3. **Conclusion**:
- Based on the analysis, transpiration is least in **(d) High atmospheric humidity**. This is because the high moisture content in the air reduces the gradient necessary for transpiration to occur effectively.

### Final Answer:
**Transpiration is least in (d) High atmospheric humidity.**

---