Which of these conclusions drawn by Cornelius van Neil in his experiment on purple -sulphur bacteria is correct ?

Options

A. He inferred that the oxygen in plants comes from water proved using radioisotope techniques.
B. He demonstrated that photosynthesis is essentially a light-independent reaction
C. In purple sulphur bacteria, the oxidation products are oxygen and sulphates
D. Water is the hydrogen donor in purple sulphur bacteria

Answer

To solve the question regarding the conclusions drawn by Cornelius van Neil in his experiment on purple-sulfur bacteria, we will analyze the key points of his findings step by step.

### Step-by-Step Solution:

1. **Understanding the Experiment**: Cornelius van Neil conducted experiments in 1931 to study photosynthesis using purple-sulfur bacteria. He aimed to understand the process of photosynthesis and the role of different substances involved.

**Hint**: Remember the context of the experiment and the organism used (purple-sulfur bacteria).

2. **Photosynthesis Mechanism**: Van Neil demonstrated that photosynthesis is a light-dependent redox reaction. This means that light is necessary for the reaction to occur, and there is a transfer of electrons (redox).

**Hint**: Focus on the terms "light-dependent" and "redox reaction" as they are crucial to understanding his conclusions.

3. **Role of Hydrogen Donor**: In his experiments, he identified that the hydrogen donor (the substance that donates hydrogen) is H2A, which in the case of purple-sulfur bacteria is hydrogen sulfide (H2S). This hydrogen donor reduces carbon dioxide (CO2).

**Hint**: Identify what the hydrogen donor is in the context of purple-sulfur bacteria.

4. **Products of Photosynthesis**: Van Neil found that when hydrogen sulfide is used, sulfur is released as a byproduct. This is different from what occurs in plants, where water is the hydrogen donor and oxygen is released as a byproduct.

**Hint**: Compare the byproducts of photosynthesis in purple-sulfur bacteria versus plants.

5. **Conclusion on Oxygen Source**: He concluded that in plants, the oxygen produced during photosynthesis comes from water (H2O), not from carbon dioxide. This was a significant finding that was later confirmed using radioisotopic techniques.

**Hint**: Remember the distinction between the source of oxygen in purple-sulfur bacteria and in plants.

6. **Evaluating the Options**: Now, let's evaluate the provided options based on the conclusions drawn by van Neil:
- **Option 1**: He inferred that the oxygen in plants comes from water, proved using radioisotopic techniques. (Correct)
- **Option 2**: He demonstrated that photosynthesis is a light-independent reaction. (Incorrect)
- **Option 3**: In purple-sulfur bacteria, the oxidation products are oxygen and sulfates. (Incorrect)
- **Option 4**: Water is the hydrogen donor in purple-sulfur bacteria. (Incorrect)

**Hint**: Carefully analyze each option against the conclusions drawn by van Neil.

### Final Answer:
The correct conclusion drawn by Cornelius van Neil in his experiment on purple-sulfur bacteria is **Option 1**: He inferred that the oxygen in plants comes from water, proved using radioisotopic techniques.