Which one will reduce rate of transpiration ?

Options

A. Rise in temperature .
B. Increase in water uptake .
C. Decrease in relative humidity .
D. Decrease in light intensity

Answer

To solve the question "Which one will reduce the rate of transpiration?", we will analyze each option provided:

1. **Understanding Transpiration**: Transpiration is the process by which water vapor is lost from the plant to the atmosphere, primarily through small openings called stomata, which are regulated by guard cells.

2. **Analyzing the Options**:
- **Option A: Rise in Temperature**: An increase in temperature generally increases the rate of transpiration because warmer air can hold more moisture, leading to a greater vapor pressure gradient between the inside of the leaf and the outside air.
- **Option B: Increase in Water Uptake**: Increasing water uptake can lead to more water being available for transpiration, potentially increasing the rate rather than reducing it.
- **Option C: Decrease in Relative Humidity**: A decrease in relative humidity increases the vapor pressure gradient, which typically increases the rate of transpiration as water moves from an area of higher concentration (inside the leaf) to lower concentration (outside).
- **Option D: Decrease in Light Intensity**: Lower light intensity reduces the rate of photosynthesis, leading to less sugar production in guard cells. This means guard cells may not gain enough turgor pressure to open the stomata fully, thus reducing transpiration.

3. **Conclusion**: Based on the analysis, the option that will reduce the rate of transpiration is **Option D: Decrease in light intensity**.

### Step-by-Step Solution:
1. **Identify the process of transpiration** and its regulation by stomata.
2. **Evaluate each option** in terms of its effect on transpiration.
3. **Determine the correct answer** based on the analysis of how each factor influences the stomatal function and transpiration rates.