Name the hormone which is used extensively in agricultural and horticultural practices and help to initiate rooting in stem cutting during plant propagation.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for a specific hormone that is widely used in agricultural and horticultural practices to promote rooting in stem cuttings during plant propagation.

2. **Identifying Plant Propagation**: Plant propagation is a method of reproduction that involves using parts of a plant, such as stems, rather than seeds. This can include techniques like stem cutting and tissue culture.

3. **Recognizing the Role of Hormones**: In plant propagation, certain hormones play a crucial role in stimulating growth and development. One of the key hormones involved in root initiation is auxin.

4. **Defining Auxin**: Auxin is a plant hormone that promotes root formation. When stem cuttings are treated with auxin, it encourages the development of roots, allowing the cutting to establish itself in the soil.

5. **Considering the Effects of Auxin**: While auxin is beneficial for root growth, it is important to note that an excess of auxin can inhibit root growth. This dual role highlights the importance of using the correct concentration of auxin in horticultural practices.

6. **Final Answer**: The hormone that is extensively used in agricultural and horticultural practices to initiate rooting in stem cuttings during plant propagation is **auxin**.

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