Hormone involved in phototropism is

Options

A. IA A
B. gibberellin
C. kinetin
D. 2,4-D

Explanation

**Step-by-Step Solution:**

1. **Understanding Phototropism**: Phototropism is the growth movement of a plant in response to light. Specifically, it refers to how plant parts, such as stems, bend towards the light source.

2. **Identifying the Hormone**: The primary hormone involved in phototropism is indole acetic acid (IAA), which is a type of auxin. Auxins are known for their role in promoting cell elongation, particularly on the side of the plant that is away from the light.

3. **Location of the Hormone**: Indole acetic acid is predominantly found at the tip of the stem. This is where it is produced and where it influences growth direction.

4. **Effect of Removing the Hormone**: If the tip of the stem, which contains indole acetic acid, is cut off (a process known as decapitation), the plant will no longer bend towards the light. This indicates that the presence of indole acetic acid is essential for the phototropic response.

5. **Conclusion**: Based on the above points, we can conclude that the hormone responsible for phototropism is indole acetic acid.

**Final Answer**: The hormone involved in phototropism is indole acetic acid.

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