Which of the following association fix nitrogen through non-nodulation?

Options

A. Roots of leguminous plants associated with Rhizobium.
B. Coralloid roots of cycas in association with Anabaena.
C. Both a and b
D. None

Answer

To solve the question "Which of the following associations fix nitrogen through non-nodulation?", we will analyze each option provided and determine whether they involve nodulation or not.

### Step-by-Step Solution:

1. **Understand Nitrogen Fixation**:
- Nitrogen fixation is the process by which nitrogen in the atmosphere is converted into ammonia or related compounds in soil. This is essential for plants as they cannot directly utilize atmospheric nitrogen.

2. **Identify the Options**:
- Option A: Roots of leguminous plants associated with Rhizobium.
- Option B: Choroid roots of Cycas in association with Anabaena.
- Option C: Both A and B.
- Option D: None of the above.

3. **Analyze Option A**:
- Leguminous plants (like peas, beans) form a symbiotic relationship with Rhizobium bacteria, which leads to the formation of nodules on the roots. These nodules are specialized structures where nitrogen fixation occurs.
- **Conclusion**: This option involves nodulation.

4. **Analyze Option B**:
- Cycas, a type of cycad, has specialized roots known as choroid roots that associate with Anabaena, a cyanobacterium. In this case, nitrogen fixation occurs without the formation of nodules.
- **Conclusion**: This option does not involve nodulation.

5. **Analyze Option C**:
- This option states that both A and B are correct. Since Option A involves nodulation and Option B does not, this option is incorrect.

6. **Analyze Option D**:
- This option states that none of the above are correct. Since we have identified that Option B is indeed a non-nodulation process, this option is also incorrect.

7. **Final Conclusion**:
- The only association that fixes nitrogen through non-nodulation is the choroid roots of Cycas in association with Anabaena.
- Thus, the correct answer is **Option B**.