Rate of transpiration is increased by

Options

A. Sunlight
B. Darkness
C. High humidity
D. High speed winds

Answer

To determine what increases the rate of transpiration, we can analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding Transpiration**:
- Transpiration is the process by which water is lost from the plant in the form of vapor. It primarily occurs through small openings in the leaves called stomata.

2. **Factors Affecting Transpiration**:
- Several environmental factors influence the rate of transpiration, including temperature, humidity, light, and wind speed.

3. **Analyzing the Options**:
- **Option A: Sunlight**:
- Sunlight increases the temperature and stimulates the opening of stomata, leading to increased transpiration. Therefore, this option is likely to increase the rate of transpiration.
- **Option B: Darkness**:
- In darkness, stomata tend to close, which reduces transpiration. Thus, this option does not increase the rate of transpiration.
- **Option C: High Humidity**:
- High humidity means there is more moisture in the air, which reduces the water vapor gradient between the inside of the leaf and the outside air. This leads to decreased transpiration. Hence, this option does not increase the rate of transpiration.
- **Option D: High Speed Winds**:
- While high winds can initially increase transpiration by removing the boundary layer of moisture around the leaf, excessive wind can lead to dehydration and stomatal closure, ultimately reducing transpiration. Therefore, this option does not consistently increase the rate of transpiration.

4. **Conclusion**:
- The only factor that consistently increases the rate of transpiration is **sunlight**. Therefore, the correct answer is **Option A: Sunlight**.

### Final Answer:
The rate of transpiration is increased by **sunlight**.

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