Histogens capping root apical meristem is

Options

A. dermatogen
B. calyptrogen
C. periblem
D. plerome

Answer

To answer the question about which histogen caps the root apical meristem, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Histogens**:
- Histogens are layers of cells in the apical meristem that give rise to different tissues in plants. They are crucial for the development of various plant organs.

2. **Identify the Types of Histogens**:
- There are three main histogens in the shoot apical meristem:
- **Dermatogen**: This is the outermost layer that develops into the epidermis.
- **Periblum**: This is the middle layer that gives rise to the cortex.
- **Plerome**: This is the innermost layer that forms the pith and vascular tissues.

3. **Recognize the Special Case of Root Apical Meristem**:
- The root apical meristem has a unique layer not found in the shoot apical meristem. This layer is called **Calyptrogen**.

4. **Define Calyptrogen**:
- Calyptrogen is the histogen responsible for forming the root cap, which protects the growing tip of the root as it pushes through the soil.

5. **Conclude the Answer**:
- Therefore, the histogen that caps the root apical meristem is **Calyptrogen** (or Calyptra).

### Final Answer:
The histogen capping the root apical meristem is **Calyptrogen**.

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