What did Engelmann observe from his prism experiments

Options

A. Bacteria could not detect the sites of `O_(2)` evolution
B. Bacteria released excess carbon dioxide in red and blue light
C. Bacteria accumulated due to increase in temperature caused by increase in `O_(2)` concentration.
D. Bacteria are accummulated towards red and blue light.

Answer

**Step-by-Step Solution:**

1. **Introduction to Engelmann's Experiment**: Engelmann conducted an experiment to determine the action spectrum of photosynthesis. He used a prism to split sunlight into its spectral components.

2. **Use of Cladophora**: In his experiment, Engelmann utilized a green alga known as Cladophora. This alga was placed in a suspension of aerobic bacteria.

3. **Splitting Light**: By splitting the sunlight into its various colors (VIBGYOR), Engelmann was able to observe how different wavelengths of light affected the process of photosynthesis.

4. **Observing Bacterial Accumulation**: Engelmann noted that the aerobic bacteria accumulated predominantly in the regions of blue and red light. This indicated that these wavelengths were most effective for photosynthesis.

5. **Relation to Chlorophyll Absorption**: Engelmann also observed that the accumulation of bacteria in blue and red light corresponded to the absorption spectra of chlorophyll A and B. This suggested that these wavelengths were critical for the photosynthetic process.

6. **Conclusion**: Engelmann concluded that the areas where the bacteria accumulated (blue and red light) were the most effective for photosynthesis, confirming the relationship between light absorption by chlorophyll and the photosynthetic activity.

**Final Answer**: Engelmann observed that bacteria accumulated towards the red and blue light in his prism experiments.

---