Who proved that oxygen evolved in photosynthesis comes from water ?

Options

A. Mayer
B. Calvin
C. Ruben and Kamen
D. Emerson

Answer

To answer the question "Who proved that oxygen evolved in photosynthesis comes from water?", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Photosynthesis**:
- Photosynthesis is the process by which green plants synthesize food using sunlight, carbon dioxide, and water. During this process, oxygen is released as a byproduct.

2. **Identifying Key Scientists**:
- The question provides four options: Mayer, Calvin, Rubin and Kamen, and Emerson. We need to identify which of these scientists conducted experiments related to the source of oxygen in photosynthesis.

3. **Research on Oxygen Source**:
- The key experiment that determined the source of oxygen in photosynthesis was conducted by scientists who used isotopes to trace the origin of oxygen. Specifically, they used radioactive oxygen isotopes.

4. **Rubin and Kamen's Experiment**:
- Rubin and Kamen used a heavy isotope of oxygen (O-18) in their experiments. They demonstrated that when water (H2O) is split during photosynthesis, the oxygen released comes from the water molecules rather than from carbon dioxide (CO2).

5. **Conclusion**:
- Based on their findings, it was concluded that the oxygen evolved during photosynthesis indeed comes from water. Therefore, the correct answer to the question is **Rubin and Kamen**.

### Final Answer:
The scientists who proved that oxygen evolved in photosynthesis comes from water are **Rubin and Kamen**.

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