The stimulus responsible for vernalization is

Options

A. Phytochrome
B. Vernalin
C. Florigen
D. None of these

Answer

**Step-by-Step Solution:**

1. **Understanding Vernalization**: Vernalization is the process by which plants require a period of cold exposure to trigger flowering. This is particularly important for certain species that need to experience winter conditions before they can flower in spring.

2. **Analyzing the Options**:
- **Option 1: Phytochrome**: Phytochrome is a photoreceptor involved in regulating various plant processes, including seed germination and flowering. However, it is not specifically responsible for the chilling requirement of vernalization.
- **Option 2: Vernaline**: This term refers to a substance associated with the vernalization process. It is believed to play a role in the physiological changes that occur in plants during the chilling treatment.
- **Option 3: Fluorogen**: Fluorogen is a flowering hormone that promotes flowering but is not involved in the vernalization process.
- **Option 4: None of these**: This option suggests that none of the previous options are correct.

3. **Conclusion**: After analyzing each option, it is clear that the stimulus responsible for vernalization is **Option 2: Vernaline**. This is because vernaline is directly related to the chilling treatment that plants undergo to initiate flowering.

**Final Answer**: The stimulus responsible for vernalization is **Vernaline**.

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