Which of the following statements incorrect about photorespiration ?

Options

A. In `C_4` plants, photorespiration does not occur.
B. In `C_3` plants, some `O_2` does not bind to `RuBisCO` , and hence `CO_2` fixation is decreased.
C. In the photorespiratory pathway , there is neither synthesis of sugars, nor of ATP
D. The biological function of photorespiration is not known yet.

Answer

To determine which statement about photorespiration is incorrect, we need to analyze each option based on our understanding of the process of photorespiration.

### Step-by-Step Solution:

1. **Understanding Photorespiration**:
- Photorespiration is a process that occurs in plants where the enzyme Rubisco fixes oxygen instead of carbon dioxide (CO2). This leads to a decrease in the efficiency of photosynthesis because it competes with the Calvin cycle, ultimately harming the plant.

2. **Analyzing the Options**:
- **Option 1**: "In C4 plants, photorespiration does not occur."
- This statement is **true**. C4 plants have a specialized anatomy (Kranz anatomy) that allows them to concentrate CO2 at the site of Rubisco, thus minimizing the chances of oxygen binding.

- **Option 2**: "In C3 plants, oxygen does not bind to Rubisco and hence CO2 fixation is decreased."
- This statement is **false**. In C3 plants, oxygen does bind to Rubisco. The problem arises because there is a lower concentration of CO2 at the enzyme site, leading to decreased CO2 fixation.

- **Option 3**: "In the photorespiratory pathway, there is neither synthesis of sugar nor of ATP."
- This statement is **true**. Photorespiration does not produce sugar or ATP, making it a wasteful process.

- **Option 4**: "The biological function of photorespiration is not known yet."
- This statement is **true**. While photorespiration is understood to be a harmful process, its exact biological significance is still under research.

3. **Conclusion**:
- The incorrect statement about photorespiration is **Option 2**: "In C3 plants, oxygen does not bind to Rubisco and hence CO2 fixation is decreased." This is incorrect because oxygen does bind to Rubisco in C3 plants.

### Final Answer:
The incorrect statement about photorespiration is: **In C3 plants, oxygen does not bind to Rubisco and hence CO2 fixation is decreased.**

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