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 from his experiments on purple-sulphur bacteria, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Experiment**: Cornelius van Neil conducted experiments on purple-sulphur bacteria between 1885 and 1897. He focused on the process of photosynthesis in these bacteria.

2. **Identify the Key Findings**: Van Neil concluded that purple-sulphur bacteria do not use water (H2O) as the source of hydrogen for photosynthesis. Instead, they use hydrogen sulfide (H2S). This is crucial because it indicates that the by-products of photosynthesis in these bacteria do not include oxygen.

3. **Photosynthesis Process**: In the photosynthesis process, van Neil demonstrated that light is essential for the reaction to occur. He indicated that photosynthesis is a light-dependent reaction where hydrogen acts as a reducing agent to convert carbon dioxide (CO2) into glucose (CH2O).

4. **Chemical Reactions**: The general reaction he proposed can be summarized as:
\[ 6CO_2 + 12H_2S \xrightarrow{\text{light}} C_6H_{12}O_6 + 12S + 6H_2 \]
This shows that sulfur (S) is released instead of oxygen (O2) when H2S is used.

5. **Evaluate the Options**: Given the conclusions drawn by van Neil, we can evaluate the provided options:
- **Option 1**: "The oxygen in plants comes from water, proved using radioisotope technique." - This is correct for plants, but not directly related to van Neil's work on purple-sulphur bacteria.
- **Option 2**: "Photosynthesis is essentially a light-independent reaction." - This is incorrect; van Neil emphasized the light-dependent nature of photosynthesis.
- **Option 3**: "In purple-sulphur bacteria, the oxidation products are oxygen and sulphates." - This is incorrect as oxygen is not produced.
- **Option 4**: "Water is the hydrogen donor in purple-sulphur bacteria." - This is incorrect; H2S is the hydrogen donor, not water.

6. **Conclusion**: The correct conclusion drawn by Cornelius van Neil is that purple-sulphur bacteria utilize hydrogen sulfide (H2S) instead of water (H2O) for photosynthesis, leading to the production of sulfur rather than oxygen.

### Final Answer:
The correct conclusion drawn by Cornelius van Neil is that purple-sulphur bacteria use H2S instead of H2O in photosynthesis, resulting in the release of sulfur instead of oxygen.