A prokaryotic autotrophic nitrogen fixing symbiont is found in

Options

A. Alnus
B. Cycas
C. Cicer
D. Pisum

Explanation

To solve the question "A prokaryotic autotrophic nitrogen-fixing symbiont is found in which of these species?", we will analyze each option provided.

### Step-by-Step Solution:

1. **Understand the Question**: We need to identify a species that has a symbiotic relationship with a prokaryotic, autotrophic, nitrogen-fixing organism.

2. **Evaluate Option A: Alnus**:
- Alnus (commonly known as alder) has a symbiotic relationship with a bacterium called *Frankia alni*.
- However, *Frankia alni* is not an autotrophic bacterium; it is a filamentous actinobacterium that fixes nitrogen but does not perform photosynthesis.
- **Conclusion**: This option is incorrect.

3. **Evaluate Option B: Cycus**:
- Cycus (likely referring to Cycas, a genus of cycads) has a symbiotic relationship with cyanobacteria such as *Nostoc* and *Anabaena*.
- Both *Nostoc* and *Anabaena* are cyanobacteria, which are prokaryotic, autotrophic, and capable of nitrogen fixation.
- **Conclusion**: This option is a strong candidate for the correct answer.

4. **Evaluate Option C: Sessile (Chickpea)**:
- Chickpea (Cicer arietinum) is a legume and has a symbiotic relationship with *Rhizobium* bacteria.
- While *Rhizobium* can fix nitrogen, it is not autotrophic; it relies on the plant for organic carbon.
- **Conclusion**: This option is incorrect.

5. **Evaluate Option D: Pisum (Peas)**:
- Peas (Pisum sativum) are also legumes and similarly have a symbiotic relationship with *Rhizobium*.
- Again, *Rhizobium* is not autotrophic, so this option is also incorrect.

6. **Final Conclusion**:
- After evaluating all options, the correct answer is **Cycus**, as it has a symbiotic relationship with autotrophic, nitrogen-fixing cyanobacteria like *Nostoc* and *Anabaena*.

### Final Answer:
**Cycus**