Name two underground and subaerial modifications of stem.

Explanation

### Step-by-Step Solution:

1. **Identify Underground Modifications of Stem**:
- The first step is to recognize that underground modifications of stems are specialized structures that grow below the soil surface.
- Two common examples of underground modifications are **tuber** and **corm**.

2. **Define Tuber**:
- A tuber is a swollen, fleshy part of a stem that serves as a storage organ. It stores nutrients, particularly starch, which the plant can use during periods of growth or dormancy.
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