T.W. Englemann determined action spectrum of photosynthesis by using

Options

A. aerobic bacteria
B. virus
C. blue green alga
D. anaerobic bacteria

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the method used by T.W. Engelmann to determine the action spectrum of photosynthesis.

2. **Identifying the Organisms Used**: Engelmann conducted his experiment using green algae, specifically *Cladophora*, and aerobic bacteria.

3. **Setting Up the Experiment**: Engelmann used a prism to split light into its spectral components. This allowed him to illuminate the green algae with different wavelengths of light.

4. **Observing Photosynthesis**: When the green algae were illuminated, they performed photosynthesis, which produced oxygen as a byproduct.

5. **Role of Aerobic Bacteria**: Engelmann placed aerobic bacteria in the vicinity of the green algae. Since these bacteria require oxygen to survive, they would accumulate in areas where oxygen concentration was highest.

6. **Analyzing Results**: Engelmann observed that the aerobic bacteria congregated mainly in the regions of blue and red light. This indicated that photosynthesis was most effective in these wavelengths, leading to higher oxygen production.

7. **Conclusion**: Engelmann's experiment successfully determined the action spectrum of photosynthesis, showing that blue and red light are the most effective wavelengths for photosynthesis.

**Final Answer**: T.W. Engelmann determined the action spectrum of photosynthesis using green algae (*Cladophora*) and aerobic bacteria.

---