The phenomenon of the influence of relative duration of day and night on flowering is called

Options

A. Vernalisation
B. Geotropism
C. Phototropism
D. Photoperiodism

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the phenomenon that describes how the relative duration of day and night affects flowering in plants.

2. **Identifying Relevant Terms**: The key terms in the question are "relative duration of day and night" and "flowering." This suggests that we are looking for a term that relates to how light and darkness influence the flowering process in plants.

3. **Analyzing the Options**:
- **A. Vernalization**: This refers to the process where flowering is induced by exposure to a prolonged period of cold temperatures. It does not relate to day and night duration.
- **B. Geotropism**: This is the growth of plants in response to gravity, not light duration.
- **C. Phototropism**: This is the growth of plants in response to light direction, but it does not involve the duration of light and darkness.
- **D. Photoperiodism**: This term refers specifically to the response of plants to the length of day and night, which directly influences flowering.

4. **Selecting the Correct Answer**: Based on the analysis, the correct answer is **D. Photoperiodism**, as it specifically addresses how the duration of light (day) and darkness (night) affects flowering in plants.

5. **Conclusion**: The phenomenon of the influence of relative duration of day and night on flowering is called **Photoperiodism**.

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