What plant tissue systems are modified by root nodule formation?

Explanation

**Step-by-Step Solution:**

1. **Understanding Root Nodules**: Root nodule formation primarily occurs in leguminous plants such as beans, peas, and peanuts. This process is essential for nitrogen fixation, which is crucial for plant growth.

2. **Symbiotic Association**: The formation of root nodules is a result of a symbiotic relationship between leguminous plants and specific bacteria known as Rhizobium. These bacteria help in converting atmospheric nitrogen into a form that plants can use.

3. **Affected Tissue Systems**: The root nodule formation modifies all three major plant tissue systems:
- **Epidermal Tissue**: The root hairs, which are part of the epidermal tissue, are modified to facilitate the penetration of Rhizobium bacteria into the root.
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