Transpiration is least affected by which environmental factors

Options

A. humidity
B. temperature
C. wind speed
D. pressure

Answer

To determine which environmental factor least affects transpiration, we can analyze each of the given factors: humidity, temperature, wind speed, and pressure.

**Step 1: Understand Transpiration**
Transpiration is the process by which plants lose water vapor through small openings called stomata. It plays a crucial role in water regulation and nutrient transport within the plant.

**Step 2: Identify the Environmental Factors**
The four environmental factors mentioned are:
1. Humidity
2. Temperature
3. Wind Speed
4. Pressure

**Step 3: Analyze Each Factor's Impact on Transpiration**
- **Humidity**: Higher humidity levels reduce the rate of transpiration because the concentration gradient between the inside of the leaf and the outside air decreases. Conversely, lower humidity increases transpiration.

- **Temperature**: Higher temperatures generally increase the rate of transpiration because they increase the rate of evaporation of water from the leaf surface.

- **Wind Speed**: Increased wind speed can enhance transpiration by removing the water vapor that accumulates around the stomata, thus maintaining a steep concentration gradient.

- **Pressure**: Atmospheric pressure has a minimal direct effect on transpiration rates. While it can influence gas exchange, it does not significantly alter the rate of water vapor loss through stomata.

**Step 4: Conclusion**
Among the four factors, pressure is the one that least affects the rate of transpiration. Therefore, the correct answer is **pressure**.

**Final Answer: Pressure (Option 4)**

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