Youngest layer of secondary growth occurs due to the activity of

Options

A. in the centre of stem
B. just outside the pith
C. just inside the vascular cambium
D. just outside the vascular cambium

Answer

To determine the youngest layer of secondary growth in a dicot stem, we need to understand the role of the vascular cambium and the arrangement of the primary and secondary tissues.

### Step-by-Step Solution:

1. **Understanding Secondary Growth**:
- Secondary growth in dicots occurs due to the activity of the vascular cambium, which is a lateral meristem. This process increases the thickness of the stem and roots.

2. **Location of Vascular Cambium**:
- The vascular cambium is located between the primary xylem (which is towards the center) and the primary phloem (which is towards the outside).

3. **Formation of Secondary Tissues**:
- As the vascular cambium divides, it produces secondary xylem (wood) towards the inside and secondary phloem towards the outside.

4. **Youngest Layer Identification**:
- The youngest layer of secondary growth is the most recently formed secondary phloem, which is located just outside the vascular cambium.

5. **Conclusion**:
- Therefore, the youngest layer of secondary growth occurs due to the activity of the vascular cambium, specifically the secondary phloem formed outside the vascular cambium.

### Final Answer:
The youngest layer of secondary growth occurs due to the activity of the vascular cambium, specifically the secondary phloem located outside the vascular cambium.

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