Cycas and Azolla plants are associated with

Options

A. Bacillus
B. Klebsiella
C. Anabaena
D. Rhizobium

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the association of Cycas and Azolla plants with specific bacteria. We need to identify which of the given options is correct.

2. **Analyzing the Options**:
- **Option A: Bacillus**: Bacillus is known to be a disease-causing bacterium. Since it does not have a known beneficial relationship with Cycas and Azolla, this option is incorrect.
- **Option B: Klebsiella**: Klebsiella is also a pathogenic bacterium that can cause diseases like pneumonia. Therefore, it is not associated with Cycas and Azolla, making this option incorrect as well.
- **Option C: Anabaena**: Anabaena is a type of cyanobacteria (commonly referred to as blue-green algae) that is known for its ability to fix atmospheric nitrogen into a usable form (ammonia). It forms a symbiotic relationship with both Cycas and Azolla, which helps in enhancing soil fertility and is used as green manure. Thus, this option is correct.
- **Option D: Rhizobium**: Rhizobium is a bacterium that forms symbiotic relationships with leguminous plants, not with Cycas and Azolla. Therefore, this option is also incorrect.

3. **Conclusion**: After evaluating all the options, the correct answer is **Option C: Anabaena**. Cycas and Azolla plants are associated with Anabaena.