The following is not a part of ground tissue system in stem

Options

A. Medulla
B. Medullary rays
C. Pericycle
D. Mesophyll

Answer

To solve the question regarding which structure is not a part of the ground tissue system in the stem, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Ground Tissue System**:
- The ground tissue system in plants consists of tissues that are neither vascular nor dermal. It includes various types of tissues that provide support, storage, and photosynthesis.

2. **Identify Components of Ground Tissue**:
- Common components of the ground tissue system in stems include:
- Cortex
- Pith (also known as medulla)
- Medullary rays
- Hypodermis
- Endodermis
- These tissues are primarily made up of parenchyma cells.

3. **Review the Options Given**:
- The options provided in the question are:
- A) Medulla
- B) Medullary rays
- C) Pericycle
- D) Mesophyll

4. **Analyze Each Option**:
- **Medulla**: This is another name for the pith, which is part of the ground tissue system.
- **Medullary Rays**: These are also part of the ground tissue system, connecting the pith and cortex.
- **Pericycle**: This is a layer of cells that can give rise to lateral roots and is considered part of the ground tissue system.
- **Mesophyll**: This tissue is found in leaves and is responsible for photosynthesis. It is not present in the stem.

5. **Conclusion**:
- Since mesophyll is specifically associated with leaves and not stems, the correct answer to the question is **D) Mesophyll**, as it is not a part of the ground tissue system in the stem.

### Final Answer:
The following is not a part of the ground tissue system in the stem: **D) Mesophyll**.