periderm includes

Options

A. cork cambium ( phellogen) cork (phellem) and secondary cortex ( phelloderm)
B. cork cambium and cork
C. cork
D. cork and secondary phloem

Answer

### Step-by-Step Solution:

1. **Understanding Periderm**:
- Periderm is a protective layer that forms during the secondary growth of plants. It replaces the epidermis in stems and roots as they increase in thickness.

2. **Components of Periderm**:
- The periderm consists of three main components:
- **Cork Cambium (Phellogen)**: This is the meristematic tissue that produces cork cells.
- **Cork (Phellum)**: This is the outer protective layer formed by the cork cambium. It is composed of dead cells that are filled with suberin, making it water-resistant.
- **Secondary Cortex (Phelloderm)**: This is the inner layer of the periderm, which is formed by the cork cambium and consists of living cells.

3. **Analyzing the Options**:
- The question provides four options regarding what the periderm includes:
- **Option 1**: Cork cambium, cork, and secondary cortex (Phellogen, Phellum, and Phelloderm).
- **Option 2**: Cork cambium and cork.
- **Option 3**: Only cork.
- **Option 4**: Cork and secondary phallum.

4. **Identifying the Correct Answer**:
- The first option is the most comprehensive as it includes all three components of the periderm: cork cambium (Phellogen), cork (Phellum), and secondary cortex (Phelloderm).
- The other options are incomplete as they do not include all three components.

5. **Conclusion**:
- Therefore, the correct answer to the question "Periderm includes" is **Option 1**: Cork cambium, cork, and secondary cortex.