Oxygenic photosynthesis is characteristic of

Options

A. Rhodospirillum
B. Spirogyra
C. Chlamydomonas
D. All of the above

Answer

To answer the question "Oxygenic photosynthesis is characteristic of," we will analyze the options provided: Rhodospirulum, Spirogyra, Chlamydomonas, or all of the above.

### Step-by-Step Solution:

1. **Understanding Photosynthesis**:
- Photosynthesis is a process used by plants, algae, and some bacteria to convert light energy into chemical energy, producing food and oxygen as by-products.

2. **Types of Photosynthesis**:
- There are two main types of photosynthesis:
- **Oxygenic Photosynthesis**: This type produces oxygen as a by-product. It is characteristic of plants, algae, and cyanobacteria.
- **Anoxygenic Photosynthesis**: This type does not produce oxygen as a by-product. It is found in some bacteria.

3. **Analyzing the Options**:
- **Rhodospirulum**: This is a type of purple non-sulfur bacteria that performs anoxygenic photosynthesis.
- **Spirogyra**: This is a green filamentous algae that performs oxygenic photosynthesis.
- **Chlamydomonas**: This is a unicellular green algae that also performs oxygenic photosynthesis.

4. **Conclusion**:
- Since Spirogyra and Chlamydomonas are both organisms that perform oxygenic photosynthesis, while Rhodospirulum does not, the correct answer to the question is **Spirogyra and Chlamydomonas**. However, since the question asks for a single characteristic organism, we can conclude that the answer is **Spirogyra and Chlamydomonas**, but not Rhodospirulum.

### Final Answer:
Oxygenic photosynthesis is characteristic of **Spirogyra and Chlamydomonas**.