Coralloid roots of Cycas has

Options

A. Anabaena
B. Aulosira
C. Mycorrhizae
D. Rhizopus

Answer

**Step-by-Step Solution:**

1. **Understanding Coralloid Roots**: Coralloid roots are specialized structures found in certain plants, particularly in Cycas. These roots are characterized by their coral-like appearance and are involved in symbiotic relationships.

2. **Identifying the Symbiotic Relationship**: The coralloid roots of Cycas form a symbiotic association primarily with cyanobacteria. This relationship is crucial for the plant's nitrogen fixation process.

3. **Recognizing the Cyanobacteria**: Among the options provided, we need to identify which cyanobacteria is associated with the coralloid roots of Cycas. The options given are:
- Anabina
- Allocera
- Mycorrhiza
- Rhizopus

4. **Evaluating the Options**:
- **Anabina**: This is a type of cyanobacteria known to associate with coralloid roots and aid in nitrogen fixation.
- **Allocera**: This is not typically associated with coralloid roots.
- **Mycorrhiza**: This refers to a symbiotic relationship between fungi and plant roots, not specifically with cyanobacteria.
- **Rhizopus**: This is a genus of fungi and does not relate to the coralloid roots of Cycas.

5. **Conclusion**: Based on the information, the correct answer is **Anabina**, as it is the cyanobacterium that forms a symbiotic relationship with the coralloid roots of Cycas for nitrogen fixation.

**Final Answer**: Anabina

---