Coralloid roots of Cycas possess a symbiotic alga

Options

A. Aulosira
B. Anabaena
C. Oscillatoria
D. Chlorella

Answer

### Step-by-Step Solution:

1. **Understanding Coralloid Roots**:
- Coralloid roots are specialized structures found in certain plants, particularly in the Cycas genus. These roots are typically found at the base of the stem and protrude above the ground.

2. **Identifying the Symbiotic Relationship**:
- Coralloid roots of Cycas are known to have a symbiotic relationship with certain algae or cyanobacteria. This relationship is beneficial for both the plant and the algae.

3. **Role of Symbiotic Algae**:
- The symbiotic algae or cyanobacteria present in the coralloid roots play a crucial role in nitrogen fixation, which is essential for the plant's nutrition.

4. **Analyzing the Options**:
- The options provided are:
- A. Allosera
- B. Anabina
- C. Oscillatoria
- D. Chlorella

5. **Evaluating Each Option**:
- **Allosera**: This is a genus of cyanobacteria that forms symbiotic relationships with hornworms, not with Cycas. Hence, this option is incorrect.
- **Anabina**: This is a genus of cyanobacteria that is known to form symbiotic relationships with plants, including Cycas. It is involved in nitrogen fixation, making this option a strong candidate.
- **Oscillatoria**: This organism reproduces by fragmentation and is typically found in freshwater environments. It does not form a symbiotic relationship with Cycas, so this option is incorrect.
- **Chlorella**: This is a green alga belonging to the Chlorophyta group, known for its photosynthetic capabilities. However, it does not have a symbiotic relationship with Cycas, making this option incorrect as well.

6. **Conclusion**:
- After evaluating all the options, the correct answer is **B. Anabina**, as it is the symbiotic alga associated with the coralloid roots of Cycas.