Inhibition photosynthesis in high concentration of oxygen is mainly due to

Options

A. distribution of RuBP carboxylase
B. inactivation of RuBP carboxylase
C. non- synthesis of RubP carboxylase
D. RuBP carboxylase acting as oxygenase

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the inhibition of photosynthesis in high concentrations of oxygen and what causes this inhibition.

2. **Identifying Key Enzyme**: The key enzyme involved in this process is RUBISCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase). This enzyme has dual functions: it can catalyze the carboxylation of ribulose-1,5-bisphosphate (RuBP) or it can act as an oxygenase.

3. **Carboxylase vs. Oxygenase Activity**:
- **Carboxylase Activity**: This is the desired reaction for photosynthesis, where RUBISCO helps fix carbon dioxide into organic molecules during the Calvin cycle (C3 cycle).
- **Oxygenase Activity**: In high oxygen concentrations, RUBISCO can mistakenly bind to oxygen instead of carbon dioxide, leading to a process called photorespiration. This process is wasteful and results in the loss of energy and carbon.

4. **Consequences of High Oxygen Concentration**: When the concentration of oxygen is high, RUBISCO's oxygenase activity increases, leading to photorespiration. This process does not contribute to photosynthesis and, in fact, inhibits it by diverting resources away from carbon fixation.

5. **Evaluating the Options**:
- **Option A**: Distribution of RUBP carboxylase - Incorrect, as this does not inhibit photosynthesis.
- **Option B**: Inactivation of RUBP carboxylase - Incorrect, as inactivation would stop photosynthesis but not inhibit it.
- **Option C**: Nonsenses of RUBP carboxylase - Incorrect, as this term does not apply to the context.
- **Option D**: RUBP carboxylase acting as oxygenase - Correct, as this leads to photorespiration and inhibits photosynthesis in high oxygen conditions.

6. **Conclusion**: The correct answer to the question is **Option D: RUBP carboxylase acting as oxygenase**.