Water pollination commonly occurs in:

Options

A. Water hyacinth
B. Lily
C. Vallisneria and Hydrilla
D. Corn cob

Answer

**Step-by-Step Solution:**

1. **Understanding Water Pollination**: Water pollination, also known as hydrophily, is a type of pollination that occurs in aquatic plants where pollen is transferred through water.

2. **Identifying Candidates for Water Pollination**: The question asks about plants that commonly exhibit water pollination. The options provided include:
- Water hyacinth
- Lily
- Valisneria
- Corn cob

3. **Analyzing Each Option**:
- **Water Hyacinth**: This plant primarily relies on insect pollination rather than water.
- **Lily**: Similar to water hyacinth, lilies are typically pollinated by insects.
- **Valisneria**: This is an aquatic plant that is known for its water pollination mechanism. Male gametes (pollen grains) are released into the water, where they swim to the female flowers located on the surface.
- **Corn Cob**: Corn is wind-pollinated, not water-pollinated.

4. **Conclusion**: Among the options, Valisneria is the only plant that commonly exhibits water pollination.

5. **Characteristics of Water Pollination in Valisneria**:
- Pollen grains are lightweight and small, allowing them to float and swim in water.
- They have a mucilaginous covering that prevents them from getting wet and sinking.
- The shape of the pollen grains is often ribbon-like, which aids in their movement through water.

Thus, the correct answer to the question is **Valisneria**.

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