cellular layers form outside to inside in old dicot stem are

Options

A. Epidermis, phellem, phellogen, phelloderm
B. Epidermis, hypodermis, cortex, endodermis
C. Epidermis, phellogen, phellem, endodermis
D. Epidermis, hypodermis, phellogen, phelloderm

Answer

To answer the question about the cellular layers from outside to inside in an old dicot stem, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Structure of an Old Dicot Stem**:
- An old dicot stem undergoes secondary growth, which results in the formation of additional layers of cells that contribute to the increase in diameter of the stem.

2. **Identifying the Layers**:
- The outermost layer of the stem is the **epidermis**. This is the protective outer layer of cells.
- Beneath the epidermis, the next layer is the **cork (phelum)**. This layer is produced by the cork cambium and serves as additional protection.
- The cork cambium itself is known as **phellogen**. It is responsible for producing the cork cells (phelum) outwardly and the secondary cortex (phelloderm) inwardly.
- Finally, the innermost layer produced by the cork cambium is the **phelloderm**. This layer is located just inside the cork and is part of the secondary cortex.

3. **Arranging the Layers from Outside to Inside**:
- Based on the above identification, the correct order of the cellular layers from outside to inside in an old dicot stem is:
- Epidermis
- Phelum (cork)
- Phellogen (cork cambium)
- Phelloderm (secondary cortex)

### Final Answer:
The cellular layers from outside to inside in an old dicot stem are:
1. Epidermis
2. Phelum (cork)
3. Phellogen (cork cambium)
4. Phelloderm (secondary cortex)

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