Apogeotropic roots in Cycas look like corals of anthozoans (coelenterata) showing mutual association with :

Options

A. Cyanobacteria
B. Bacteria
C. Fungi
D. Obligate parasite

Answer

### Step-by-Step Solution:

1. **Understanding Apogeotropic Roots**:
- Apogeotropic roots are specialized roots that grow upwards instead of downwards, which is typical for most roots. In the case of Cycas, these roots are also referred to as choreloid roots because they resemble corals.

2. **Identifying the Plant**:
- The plant in question is Cycas, which is a genus of cycads. These plants have unique root structures that allow them to adapt to their environment.

3. **Recognizing the Mutual Association**:
- The question asks about the mutual association of these roots. In Cycas, the apogeotropic roots have a symbiotic relationship with certain organisms.

4. **Identifying the Symbiotic Organism**:
- The organism that forms a mutual association with the apogeotropic roots of Cycas is a type of cyanobacteria known as Anabaena cycady. This organism is crucial for nitrogen fixation.

5. **Understanding Nitrogen Fixation**:
- Nitrogen fixation is the process by which nitrogen in the atmosphere is converted into ammonia or related compounds in soil and water, which is essential for plant growth. Anabaena cycady helps Cycas by providing it with fixed nitrogen.

6. **Conclusion**:
- Therefore, the correct answer to the question is that the apogeotropic roots in Cycas show mutual association with **Anabaena cycady**.