Discoid stem is found in
A. Pistia B. Allium
C. Potato D. Dolichos

Options

A. A only
B. A and B only
C. A and C only
D. A, B, C and D

Answer

To determine which plant has a discoid stem, we need to analyze each option provided in the question.

1. **Understanding Discoid Stem**: A discoid stem is a type of stem that is found just above the base of the root. It is typically associated with certain plants that have a specific growth form.

2. **Analyzing Each Option**:
- **A. Pistia**: This plant, commonly known as water lettuce, has a structure that forms just above the root base. Therefore, it is classified as having a discoid stem.
- **B. Allium**: Allium refers to onions, which also exhibit a structure that forms just above the root base. Thus, Allium is also classified as having a discoid stem.
- **C. Potato**: Potatoes are tubers that store nutrients and do not have a discoid stem. They grow underground and do not fit the definition of a discoid stem.
- **D. Dolichos**: This flowering plant grows high above the soil and does not exhibit discoid stem formation.

3. **Conclusion**: Based on the analysis, both Pistia and Allium exhibit discoid stems. However, since the question asks for the plant that specifically has a discoid stem, the correct answer is:
- **A. Pistia** and **B. Allium** are both correct, but if we are to choose one option, we can consider **A. Pistia** as the primary example.

### Final Answer:
The discoid stem is found in **A. Pistia** and **B. Allium**.