Photoperiodism : Florigen :: Vernalization ........

Explanation

To solve the analogy "Photoperiodism : Florigen :: Vernalization ........", we need to understand the relationships between the terms involved.

### Step-by-Step Solution:

1. **Understanding Photoperiodism**:
- Photoperiodism is the response of plants to the length of day and night. It influences various developmental processes in plants, particularly flowering.

2. **Identifying Florigen**:
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