An antitranspirant is

Options

A. Cobalt chaloride
B. Mercury
C. Potassium
D. Phenyl mercuric acetate.

Answer

**Step-by-Step Solution:**

1. **Understanding Antitranspirants**: Antitranspirants are chemical compounds that are applied to the leaves of plants to reduce the rate of transpiration, which is the loss of water vapor from the plant.

2. **Function of Antitranspirants**: These compounds work by decreasing the size and number of stomata, which are the small openings on the leaf surface that facilitate gas exchange and transpiration.

3. **Importance of Antitranspirants**: They are particularly useful in agriculture and horticulture to conserve water, especially in conditions where water is scarce or costly. They help in maintaining crop yield under water stress conditions.

4. **Identifying the Correct Antitranspirant**: Among the options provided (cobalt, chloride, mercury, potassium, phenyl mercuric acetate), we need to identify which one is recognized as an antitranspirant.

5. **Example of an Antitranspirant**: Phenyl mercuric acetate (PMA) is a well-known antitranspirant. It not only inhibits the opening of stomata but can also reduce the photosynthetic rate and overall growth of the plant.

6. **Conclusion**: Based on the information, the correct answer to the question "An antitranspirant is" is **phenyl mercuric acetate**.

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