Secondary growth occurs due to activity of -

Options

A. Cork cambium
B. Interfascicular cambium
C. Vascular cambium
D. Both a and c

Answer

**Step-by-Step Solution:**

1. **Understanding Secondary Growth**: Secondary growth refers to the increase in thickness or girth of a plant, primarily occurring in woody plants. This growth is essential for the plant's structural support and is distinct from primary growth, which increases the length of the plant.

2. **Identifying the Tissues Involved**: The primary tissues responsible for secondary growth are the cambium layers. The two main types of cambium involved in secondary growth are:
- **Cork Cambium**: This layer produces cork cells, which form the outer protective layer of the plant.
- **Vascular Cambium**: This layer is responsible for the production of secondary xylem (wood) and secondary phloem (inner bark).

3. **Analyzing the Options**:
- **Option 1: Cork Cambium**: This is involved in secondary growth as it produces cork on the outer side and secondary cortex on the inner side. Therefore, this option is correct.
- **Option 2: Interfascicular Cambium**: This is formed from the division of medullary rays and connects two vascular cambium regions. However, it is not the primary cause of secondary growth, making this option incorrect.
- **Option 3: Vascular Cambium**: This is indeed a major contributor to secondary growth as it produces secondary xylem and phloem. Therefore, this option is also correct.
- **Option 4: Both A and C**: Since both cork cambium and vascular cambium are involved in secondary growth, this option is correct.

4. **Conclusion**: The correct answer to the question is that secondary growth occurs due to the activity of both cork cambium and vascular cambium.

**Final Answer**: Secondary growth occurs due to the activity of both cork cambium and vascular cambium (Option 4).

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