Who used prism, green alga Cladophora and aerobic bacteria and plotted the first action spectrum of photosynthesis?

Options

A. Sachs
B. Amon
C. Arnold
D. Engelmann

Explanation

To answer the question of who used a prism, the green alga Cladophora, and aerobic bacteria to plot the first action spectrum of photosynthesis, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Components Used in the Experiment**: The experiment involved a prism, green alga Cladophora, and aerobic bacteria. The prism was used to split light into its component wavelengths.

2. **Understand the Purpose of the Experiment**: The goal was to investigate the effect of different wavelengths of light on photosynthesis. By splitting the light, the researcher aimed to see which wavelengths were most effective for photosynthesis.

3. **Describe the Setup**: The illuminated Cladophora (green alga) was placed in a suspension of aerobic bacteria. This setup allowed the researcher to observe the behavior of the bacteria in relation to the light spectrum.

4. **Observe the Results**: The key observation was that the aerobic bacteria accumulated in the regions of blue and red light. This indicated that these wavelengths were more effective for photosynthesis.

5. **Conclude the Findings**: From these observations, the researcher concluded the effect of different wavelengths of light on photosynthesis and subsequently plotted the first action spectrum of photosynthesis.

6. **Identify the Researcher**: The researcher who conducted this experiment and plotted the first action spectrum of photosynthesis was Engelmann.

### Final Answer:
The person who used a prism, green alga Cladophora, and aerobic bacteria to plot the first action spectrum of photosynthesis was **Engelmann**.

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