The well developed root system of Pistia serves to absorb water.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Plant:**
- Pistia is an aquatic plant commonly known as water lettuce. It thrives in water bodies and has specific adaptations that allow it to survive in such environments.

2. **Analyzing the Root System:**
- The root system of Pistia is well-developed, but its primary function is not solely to absorb water. Instead, it has adaptations that serve multiple purposes.

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