Drooping of Tamarind leaves after sunset is

Options

A. Phototropism
B. Phototaxis
C. Photonasty
D. Chemotaxis.

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the phenomenon of tamarind leaves drooping after sunset. This indicates a specific type of movement or response in plants.

2. **Identifying the Options**: The options provided are:
- Phototropism
- Phototaxis
- Photonasty
- Chemotaxis

3. **Defining Each Term**:
- **Phototropism**: This refers to the growth of a plant in response to light direction. Plants bend towards light sources.
- **Phototaxis**: This is the movement of an organism towards or away from light. It is primarily observed in motile organisms, not in plants.
- **Photonasty**: This refers to a non-directional movement in response to light, such as the opening and closing of flowers or leaves, regardless of the light source's direction.
- **Chemotaxis**: This is the movement of an organism in response to chemical stimuli, not applicable to the question.

4. **Analyzing the Phenomenon**: The drooping of tamarind leaves after sunset is a response to the absence of light. This is not a directional movement but rather a reaction to the change in light conditions.

5. **Conclusion**: Since the drooping of the leaves is a non-directional response to the absence of light, it is best described by the term **Photonasty**. Therefore, the correct answer is **Photonasty**.