Phototropic curvature is the result of uneven distribution of

Options

A. gibberellins
B. phytochrome
C. cytokinins
D. auxin

Answer

**Step-by-Step Text Solution:**

1. **Understanding Phototropism**: Phototropism is the growth of a plant in response to light direction. When light shines on one side of a plant, it causes the plant to bend towards the light.

2. **Role of Phytohormones**: The bending of the plant towards the light is due to the action of phytohormones, which are chemical substances that regulate plant growth and development.

3. **Identifying the Correct Phytohormone**: Among the options provided, we need to identify which phytohormone is responsible for the uneven growth that results in phototropic curvature.

4. **Evaluating the Options**:
- **Gibberellins**: These are involved in seed germination and stem elongation but do not directly cause phototropic curvature. (Incorrect)
- **Phytochrome**: This is a pigment that helps plants detect light but does not cause curvature. (Incorrect)
- **Cytokinins**: These hormones promote cell division and are not primarily responsible for phototropic responses. (Incorrect)
- **Auxin**: This hormone plays a crucial role in phototropism by promoting cell elongation on the side of the plant that is away from the light, leading to curvature towards the light. (Correct)

5. **Conclusion**: The uneven distribution of auxin on the sides of the plant leads to differential growth rates, causing the plant to bend towards the light source.

**Final Answer**: Phototropic curvature is the result of uneven distribution of **Auxin**.

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