With decrease in atmospheric pressure the rate of transpiration will :

Options

A. Remain unaffected
B. Increased
C. Decrease slowly
D. Decrease rapidly

Answer

To solve the question "With decrease in atmospheric pressure the rate of transpiration will:", we can follow these steps:

### 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. **Effect of Atmospheric Pressure**: Atmospheric pressure plays a significant role in the rate of transpiration. When atmospheric pressure decreases, the external pressure on the water vapor inside the leaf also decreases.

3. **Water Vapor Concentration**: A decrease in atmospheric pressure leads to a lower concentration of water vapor in the air surrounding the plant. This creates a steeper gradient for water vapor to diffuse out of the leaf.

4. **Increased Rate of Transpiration**: Due to the steeper gradient created by lower atmospheric pressure, the rate of transpiration increases. The plant will lose more water vapor as it moves from an area of higher concentration (inside the leaf) to an area of lower concentration (the atmosphere).

5. **Conclusion**: Therefore, with a decrease in atmospheric pressure, the rate of transpiration will increase.

### Final Answer:
The correct answer is that the rate of transpiration will **increase** with a decrease in atmospheric pressure.

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