Which pollutant causes leaf curling?

Options

A. CO
B. `H_(2)S`
C. `O_(3)`
D. `SO_(2)`

Answer

**Step-by-Step Solution:**

1. **Identify the Pollutants:**
The question provides four options: CO (Carbon Monoxide), H2S (Hydrogen Sulfide), O3 (Ozone), and SO2 (Sulfur Dioxide).

2. **Analyze Each Option:**
- **CO (Carbon Monoxide):**
- It causes premature abscission (the dropping of leaves or ripe fruits) and yellowing of leaves.
- **Conclusion:** This does not cause leaf curling.

- **H2S (Hydrogen Sulfide):**
- This gas causes defoliation, which is the falling off of leaves.
- **Conclusion:** This does not cause leaf curling.

- **O3 (Ozone):**
- Ozone causes hindrance in mitochondrial function but does not specifically mention leaf curling.
- **Conclusion:** This does not cause leaf curling.

- **SO2 (Sulfur Dioxide):**
- Sulfur dioxide is a major air pollutant from vehicular and industrial emissions.
- It has a deleterious effect on plant leaves, causing bleaching of chlorophyll (leading to chlorosis) and inward curling of leaves along the margins.
- **Conclusion:** This causes leaf curling.

3. **Final Answer:**
Based on the analysis, the pollutant that causes leaf curling is **SO2 (Sulfur Dioxide)**.

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