Water plants usually have well developed

Options

A. root system
B. stem
C. vascular system
D. leaves

Answer

To answer the question "Water plants usually have well developed," we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Type of Plants**: Water plants, also known as aquatic plants, can be categorized into two main types: submerged plants and free-floating plants.

2. **Understand the Structures of Aquatic Plants**: Aquatic plants have various structures including roots, stems, vascular systems, and leaves. Each of these structures plays a role in the plant's adaptation to its environment.

3. **Focus on Leaf Modifications**: Among the structures, the leaves of aquatic plants show significant modifications. The leaves consist of three parts: the leaf base, petiole, and lamina.

4. **Examine the Petiole**: The petiole is the stalk that connects the leaf to the stem. In aquatic plants, the petiole is often swollen and contains air chambers. This adaptation is crucial for buoyancy.

5. **Role of Buoyancy**: The presence of air chambers and spongy tissues in the petiole allows free-floating aquatic plants to maintain their position on the water's surface, facilitating access to sunlight for photosynthesis.

6. **Conclusion**: Therefore, the well-developed structure in water plants is primarily the leaves, specifically the petiole, which has adaptations that enable buoyancy.

### Final Answer:
Water plants usually have well-developed **leaves** (especially the petiole).

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