Which of the following is correct about legumes?

Options

A. They are incapable of fixing nitrogen
B. They fix nitrogen with the help of bacteria that live in their leaves
C. They fix nitrogen with the help of bacteria that live in their root
D. They fix nitrogen independent of bacteria.

Answer

**Step-by-Step Solution:**

1. **Understanding Legumes:**
- Legumes are a group of plants that belong to the family Fabaceae. They are known for their ability to fix nitrogen from the atmosphere into a form that can be used by plants.

2. **Nitrogen Fixation:**
- Nitrogen fixation is the process by which nitrogen (N2) in the atmosphere is converted into ammonia (NH3) or related compounds in soil and water. This is crucial for plant growth as nitrogen is an essential nutrient.

3. **Symbiotic Relationship:**
- Legumes form a symbiotic relationship with nitrogen-fixing bacteria, primarily from the genus Rhizobium. This means that both the legumes and the bacteria benefit from each other.

4. **Location of Bacteria:**
- The nitrogen-fixing bacteria (Rhizobium) invade the root hairs of leguminous plants. They form specialized structures called root nodules where the nitrogen fixation process occurs.

5. **Analyzing the Options:**
- **Option 1:** "They are incapable of fixing nitrogen." - This is incorrect because legumes can fix nitrogen.
- **Option 2:** "They fix nitrogen with the help of bacteria that live in their leaves." - This is incorrect because the bacteria live in the roots, not the leaves.
- **Option 3:** "They fix nitrogen with the help of bacteria that live in their root." - This is correct as the bacteria reside in root nodules.
- **Option 4:** "They fix nitrogen independent of bacteria." - This is incorrect because legumes rely on bacteria for nitrogen fixation.

6. **Conclusion:**
- The correct answer is **Option 3:** "They fix nitrogen with the help of bacteria that live in their root."

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