Vernalization is defined as

Options

A. all changes that an organism goes through during its life cycle.
B. flowering that is either quantitatively or qualitatively dependent on the exposure to low temperature.
C. flowering induced only when a plant is exposed to certain duration of photoperiod .
D. presence of different kinds of structure in response to environment or phases of life .

Answer

To solve the question regarding the definition of vernalization, we will analyze each option provided and determine which one correctly defines the term.

### Step-by-Step Solution:

1. **Understanding Vernalization**: Vernalization is a process that involves the exposure of plants to a prolonged period of cold temperatures, which is necessary for them to flower. This is particularly important for certain plants that require this cold treatment to trigger their flowering process.

2. **Analyzing Option A**:
- Option A states: "All changes that an organism goes through during its life cycle."
- This definition refers to the overall development of an organism, not specifically to the flowering process or the influence of temperature. Therefore, this option is incorrect.

3. **Analyzing Option B**:
- Option B states: "Flowering that is quantitatively or qualitatively dependent on exposure to the low temperature."
- This option directly relates to the process of vernalization, as it highlights the dependence of flowering on exposure to low temperatures. This is the correct definition of vernalization.

4. **Analyzing Option C**:
- Option C states: "Flowering should be induced only when the plant is exposed to a certain duration of water period."
- This option focuses on water exposure rather than temperature. Vernalization specifically involves cold temperatures, making this option incorrect.

5. **Analyzing Option D**:
- Option D states: "Presence of different kinds of structures in response to environmental or phases of life."
- This option refers to plasticity in plants, which is not related to the specific process of vernalization. Thus, this option is also incorrect.

6. **Conclusion**:
- After analyzing all options, we find that Option B accurately defines vernalization. Therefore, the answer is:
- **Correct Answer**: Option B - "Flowering that is quantitatively or qualitatively dependent on exposure to the low temperature."