Which hormone level increases during vernalisation?

Answer

**Step-by-Step Solution:**

1. **Understanding Vernalization**: Vernalization is the process where plants or seeds are exposed to low temperatures for a certain period. This exposure is artificial and is done to stimulate flowering and enhance seed production.

2. **Purpose of Vernalization**: The main purpose of vernalization is to satisfy the cold requirement of many plants, which is necessary for them to flower and produce seeds effectively.

3. **Effects of Vernalization**: The advantages of vernalization include:
- Increased plant yield.
- Enhanced resistance to cold and diseases.
- The ability for plants to grow in regions where they typically would not thrive.
- Enabling biennial plants to behave like annual plants (i.e., flowering and producing seeds in one year instead of two).

4. **Hormonal Changes During Vernalization**: During the process of vernalization, there is an increase in the levels of certain plant hormones.

5. **Identifying the Key Hormone**: The hormone that is primarily responsible for the effects of vernalization is **gibberellins**. Gibberellins play a crucial role in promoting plant growth and are involved in the flowering process.

6. **Conclusion**: Therefore, the hormone level that increases during vernalization is **gibberellins**.

---