Name a plant hormone that exist in gaseous state.

Answer

**Step-by-Step Solution:**

1. **Identify the Requirement:** The question asks for a plant hormone that exists in a gaseous state.

2. **Recall Plant Hormones:** There are several plant hormones, but they can be classified into different states: gaseous, liquid, and solid.

3. **Focus on Gaseous Hormones:** Among the plant hormones, one notable hormone is ethylene, which is known to exist in a gaseous form.

4. **Understand Ethylene's Role:** Ethylene is often referred to as the "ripening hormone" because it plays a crucial role in the ripening of fruits.

5. **Production of Ethylene:** Ethylene is produced in ripening fruits, and it can also be found in flowers, leaves, and roots of plants.

6. **Functions of Ethylene:** This hormone initiates various physiological changes in fruits, such as:
- Softening of the fruit texture.
- Change in color as the fruit ripens.
- Inducing leaf abscission (shedding of leaves).
- Promoting seed germination.
- Encouraging leaf and flower senescence (aging process).

7. **Conclusion:** Therefore, the plant hormone that exists in a gaseous state is ethylene.

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