One of the following modifications of Eichhornia species. Useful for vegetative propagation.

Options

A. Root
B. Aerial stem
C. Underground stem
D. Subaerial stem

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the modification of Eichhornia species (commonly known as water hyacinth) that is useful for vegetative propagation.

2. **Defining Vegetative Propagation**: Vegetative propagation is a form of asexual reproduction where new plants grow from parts of the parent plant, such as stems, leaves, or buds, rather than from seeds.

3. **Identifying the Plant**: Eichhornia species, or water hyacinth, is a floating aquatic plant that reproduces vegetatively.

4. **Examining Plant Modifications**: We need to analyze the different parts of the Eichhornia plant to determine which part is involved in vegetative propagation:
- **Roots**: These are submerged in water and do not contribute to vegetative propagation.
- **Aerial Stems**: These are above the water and provide support but are not the primary means of propagation.
- **Underground Stems**: These are not present in Eichhornia species.
- **Sub-aerial Stems**: These are stems that grow just above the surface of the water and can propagate new plants.

5. **Conclusion**: The modification of Eichhornia species that is useful for vegetative propagation is the **sub-aerial stem**. This part can be cut and placed in another location, allowing new plants to grow.

6. **Final Answer**: The correct option is **sub-aerial stem**.

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