Who demonstrated for the first time that in photosynthesis, oxygen is evolved from water

Options

A. Ruben and Kamen
B. Calvin
C. R. Hill
D. Govindji

Answer

**Step-by-Step Solution:**

1. **Identify the Key Experiment**: The question asks who first demonstrated that oxygen is evolved from water during photosynthesis. The key experiment to consider is the one conducted by Robert Hill in 1939.

2. **Understand the Experimental Setup**: Hill used chloroplasts extracted from the leaves of two specific plants: Stellaria media and Lamium album. These chloroplasts were suspended in a test tube.

3. **Components of the Experiment**: The test tube contained suitable electron acceptors and potassium ferrocyanide. These components were crucial for the experiment as they facilitated the photochemical reactions.

4. **Observation of Oxygen Release**: When exposed to light, the chloroplasts underwent a process known as photochemical splitting of water. This process resulted in the release of oxygen.

5. **No Carbon Dioxide Consumption**: It is important to note that during this experiment, no carbon dioxide was consumed, and no carbohydrates (like glucose) were formed. This indicates that the experiment was focused solely on the release of oxygen from water.

6. **Conclusion**: Robert Hill's experiment provided the first evidence that oxygen released during photosynthesis comes from the splitting of water molecules, rather than from carbon dioxide.

**Final Answer**: Robert Hill demonstrated for the first time that in photosynthesis, oxygen is evolved from water in 1939.

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