The first experiment on photosynthesis in flashing light were carried out by

Options

A. Hill
B. Calvin
C. Blackman
D. Emerson and Arnold.

Answer

**Step-by-Step Solution:**

1. **Identify the Question**: The question asks about the first experiment on photosynthesis conducted with flashing light.

2. **Review the Options**: The options provided include:
- Hill
- Calvin
- Blackman
- Emerson and Arnold

3. **Evaluate Each Option**:
- **Hill**: Robert Hill is known for his work on the oxygen evolution during photosynthesis but did not use flashing light in his experiments. Thus, he is not the correct answer.
- **Calvin**: Melvin Calvin is recognized for the Calvin cycle, which describes the light-independent reactions of photosynthesis. He did not conduct experiments with flashing light, making him an incorrect choice.
- **Blackman**: Frederick Frost Blackman studied the light and dark reactions of photosynthesis. His work focused on the dark reactions, which are independent of light. Therefore, he did not use flashing light and is not the correct answer.
- **Emerson and Arnold**: They conducted experiments using flashing light of high intensity and varied chlorophyll content in cells. Their findings related to the amount of chlorophyll per molecule of carbon dioxide and its relation to the light reactions of photosynthesis.

4. **Conclusion**: Based on the evaluations, the correct answer is **Emerson and Arnold**, as they were the first to experiment with flashing light in the context of photosynthesis.

**Final Answer**: Emerson and Arnold

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