Secondary growth in extrasteler region is due to activity of

Options

A. Interfascicular cambium
B. Intrafascicular cambium
C. Cork cambium
D. Intercalary meristem

Answer

**Step-by-Step Solution:**

1. **Understanding Secondary Growth**: Secondary growth refers to the increase in the thickness of stems and roots in plants, which occurs after the primary growth phase. This growth is primarily due to the activity of certain types of meristematic tissues.

2. **Identifying the Options**: The question provides four options regarding which tissue is responsible for secondary growth in the extrastelar region:
- Interfascular cambium
- Interfascular cambium (noted twice, likely a typographical error)
- Cork cambium
- Intercalary meristem

3. **Evaluating Interfascular Cambium**: The interfascular cambium is located between the vascular bundles in the stem. While it contributes to the formation of vascular tissues, it does not primarily drive secondary growth in the extrastelar region.

4. **Evaluating Cork Cambium**: The cork cambium is a lateral meristem that produces cork cells on the outer side and phelloderm (cortex) on the inner side. This activity contributes significantly to secondary growth as it helps in forming protective layers and increases the girth of the plant.

5. **Evaluating Intercalary Meristem**: The intercalary meristem is found at the base of leaves or internodes and is responsible for primary growth, not secondary growth. This type of meristem is involved in elongation rather than thickening.

6. **Conclusion**: Based on the evaluations, the cork cambium is the correct answer as it is responsible for secondary growth in the extrastelar region by producing cork and phelloderm.

**Final Answer**: Cork cambium is responsible for secondary growth in the extrastelar region.

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