Which is an example of secondary meristem ?

Options

A. Xylem
B. Phloem
C. Epidermis
D. Cork cambium

Answer

To determine which is an example of a secondary meristem, let's analyze the options provided:

1. **Xylem**: Xylem is a complex permanent tissue responsible for the transport of water and minerals in plants. It is not a meristematic tissue, as it does not have the capability to divide and form new cells.

2. **Phloem**: Similar to xylem, phloem is also a complex permanent tissue that transports nutrients, particularly sugars, throughout the plant. Like xylem, it does not function as a meristematic tissue.

3. **Epidermis**: The epidermis is a protective layer that forms the outer covering of the plant. It is part of the epidermal tissue system and does not have the ability to divide and form new cells, thus it is not a secondary meristem.

4. **Cork cambium**: Cork cambium is a type of secondary meristem. It is responsible for the production of cork cells, which contribute to the protective outer layer of the plant and increase the girth of stems and roots. This meristematic tissue allows for secondary growth, which is an increase in the diameter of the plant.

Based on the analysis above, the correct answer is **cork cambium**.

### Step-by-step Solution:
1. **Identify the options**: The question provides four options: xylem, phloem, epidermis, and cork cambium.
2. **Analyze each option**:
- Xylem: Complex permanent tissue, not a meristem.
- Phloem: Complex permanent tissue, not a meristem.
- Epidermis: Protective layer, part of the epidermal tissue system, not a meristem.
- Cork cambium: A secondary meristem responsible for secondary growth.
3. **Determine the correct answer**: Cork cambium is the only option that qualifies as a secondary meristem.