when secondary growth occurs, girth of stem increases. Cambial ring increases in diameter due to

Options

A. periclinal deivision and radial elongation of cambial cells
B. anticlinal divison and radial eleongations of cambial cells
C. both periclinal and anticlinal divisons and radial elongation of cambial cells
D. radial elongation of cambium cells along.

Answer

To answer the question regarding the increase in the diameter of the cambial ring during secondary growth in plants, we can break down the explanation into several steps:

### Step-by-Step Solution:

1. **Understanding Secondary Growth**:
- Secondary growth refers to the increase in the girth of stems and roots in plants, primarily due to the activity of the cambium.

2. **Role of Cambium**:
- The cambium is a layer of meristematic tissue that is responsible for the production of secondary vascular tissues. It forms a ring known as the vascular cambium.

3. **Types of Cell Division**:
- Cambial cells can undergo two types of divisions:
- **Periclinal Division**: This is the division of cambial cells parallel to the surface, which results in the formation of new cells that contribute to the increase in girth.
- **Anticlinal Division**: This division occurs perpendicular to the surface and mainly increases the number of cambial cells without significantly contributing to the increase in girth.

4. **Radial Elongation**:
- In addition to cell division, cambial cells also undergo radial elongation, which further contributes to the increase in the diameter of the cambial ring.

5. **Formation of Secondary Tissues**:
- The new cells produced through periclinal division differentiate into secondary xylem (wood) and secondary phloem (part of the bark), leading to an overall increase in the girth of the stem.

6. **Conclusion**:
- Therefore, the increase in the diameter of the cambial ring during secondary growth is primarily due to **periclinal division** and **radial elongation** of cambial cells.

### Final Answer:
The cambial ring increases in diameter due to **periclinal division and radial elongation of cambial cells**.

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