First action spectrum of photosynthesis based on study of Cladophora was given by -

Options

A. Jan ingenuous
B. Joseph Priestley
C. Von Sachs
D. Engelmann

Answer

To answer the question about the first action spectrum of photosynthesis based on the study of Cladophora, we need to follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Action Spectrum**: The action spectrum of photosynthesis refers to the effectiveness of different wavelengths of light in driving the process of photosynthesis. It is typically determined by measuring the rate of photosynthesis at different wavelengths.

2. **Identify Cladophora**: Cladophora is a genus of green algae. Studies on this algae have contributed significantly to our understanding of photosynthesis and its action spectrum.

3. **Research Historical Contributions**: The first action spectrum of photosynthesis was established through experiments conducted by scientists. One of the notable figures in this research is **Theodor Engelmann**.

4. **Engelmann's Experiment**: Engelmann used Cladophora in his experiments to determine which wavelengths of light were most effective for photosynthesis. He used a prism to disperse light and observed the growth of aerobic bacteria in relation to the light spectrum, concluding that the blue and red wavelengths were most effective.

5. **Conclusion**: Based on Engelmann's work with Cladophora, we can conclude that he was the scientist who provided the first action spectrum of photosynthesis.

### Final Answer:
The first action spectrum of photosynthesis based on the study of Cladophora was given by **Theodor Engelmann**.