the outer cellular complex present on the outside of those stems and roots which have undergone secondary growth is

Options

A. periderm
B. epiblema
C. phelloderm
D. phellogen

Answer

To answer the question about the outer cellular complex present on the outside of stems and roots that have undergone secondary growth, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Secondary Growth**: Secondary growth occurs in certain plants, particularly dicots, where the plant increases in thickness. This growth is facilitated by the activity of the vascular cambium and cork cambium.

2. **Identify the Outer Cellular Complex**: During secondary growth, the outer layer of the stem and root is modified. This layer is not the original epidermis but a new protective layer that forms as the plant grows thicker.

3. **Define the Periderm**: The outer cellular complex that forms during secondary growth is known as the periderm. It consists of three main components:
- **Cork (Phellem)**: The outermost layer that provides protection.
- **Cork Cambium (Phellogen)**: The meristematic tissue that produces cork cells.
- **Phelloderm**: The layer of parenchyma cells formed inwardly from the cork cambium.

4. **Differentiate from Other Options**:
- **Epiblema**: This is the epidermis with root hairs, primarily found in roots, not in stems undergoing secondary growth.
- **Phalloderm**: This refers to the parenchymatic tissue formed towards the inner side of the cork cambium, not the outer layer.
- **Phallogens**: These are meristematic tissues that contribute to the formation of the periderm but are not the outer layer themselves.

5. **Conclusion**: Based on the definitions and functions of the layers involved in secondary growth, the correct answer to the question is **periderm**.

### Final Answer:
The outer cellular complex present on the outside of those stems and roots which have undergone secondary growth is called **periderm**.