Effect of day length duration duration of plant development is .

Options

A. Chemotropism
B. Phototropism
C. Photoperidism
D. Photonasty

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the effect of day length duration on plant development. This implies we need to identify a term that describes how plants respond to varying lengths of light and dark periods.

2. **Identifying Key Terms**: The key terms in the question are "day length duration" and "plant development." These terms are crucial in understanding the concept of how plants react to light conditions.

3. **Exploring the Options**: The options provided are:
- Option A: Chemotropism
- Option B: Phototropism
- Option C: Photoperiodism
- Option D: Phototensility

4. **Defining Each Option**:
- **Chemotropism**: This refers to the growth of a plant in response to a chemical stimulus.
- **Phototropism**: This is the growth of a plant towards light.
- **Photoperiodism**: This is the developmental response of plants to the relative lengths of light and dark periods. It directly relates to how day length affects flowering and other developmental processes.
- **Phototensility**: This term is not commonly used in plant biology and does not relate to the concept of day length.

5. **Choosing the Correct Answer**: Given the definitions, photoperiodism (Option C) is the correct term that describes the effect of day length on plant development. It encompasses how plants respond to the duration of light and darkness, influencing their growth and flowering.

6. **Final Answer**: The effect of day length duration on plant development is known as **Photoperiodism** (Option C).