Name the external factors which affect the rate of transpiration

Answer

**Step-by-Step Text Solution:**

1. **Definition of Transpiration**: Transpiration is the process by which plants lose water in the form of water vapor through small openings called stomata, primarily located on the leaves.

2. **Identification of External Factors**: The rate of transpiration is influenced by several external or atmospheric factors. These factors include:

- **Light**:
- Directly affects the opening of stomata; more light leads to more stomata being open.
- Indirectly raises temperature, which increases transpiration rates.
- Absence of light causes stomata to close, reducing transpiration.

- **Wind**:
- Increased wind velocity removes humid air from around the leaves and replaces it with drier air, enhancing the rate of transpiration.

- **Availability of Soil Water**:
- Sufficient soil water is crucial; a decrease in available soil water can reduce transpiration rates, but only to a certain extent.

- **Temperature**:
- Higher temperatures lower the relative humidity of the atmosphere, which can increase the rate of transpiration.

- **Atmospheric Pressure**:
- A reduction in atmospheric pressure can lead to an increase in the rate of transpiration.

- **Humidity**:
- Increased humidity in the atmosphere reduces the rate of transpiration, while decreased humidity increases it.

3. **Conclusion**: The main external factors affecting the rate of transpiration are light, wind, availability of soil water, temperature, atmospheric pressure, and humidity.

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