Name the hormone which regulate abscission and dormancy.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the name of the hormone that regulates two specific processes in plants: abscission and dormancy.

2. **Identifying the Hormone**: The hormone that is primarily responsible for regulating abscission (the shedding of plant parts) and dormancy (the state of inactivity in seeds or buds) is known as abscisic acid.

3. **Role of Abscisic Acid in Abscission**: Abscisic acid plays a crucial role in the process of abscission by signaling the plant to shed its leaves, fruits, or flowers, especially when the plant is under stress or when these parts are no longer needed.

4. **Role of Abscisic Acid in Dormancy**: This hormone also promotes dormancy in seeds and buds, particularly under unfavorable conditions such as drought or extreme temperatures. It helps the plant to conserve resources and survive until conditions improve.

5. **Conclusion**: Therefore, the hormone that regulates both abscission and dormancy in plants is abscisic acid.

**Final Answer**: Abscisic acid.

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