In `C_(4)` plants there is no photorespiration because :

Options

A. The have large number of chloroplast
B. increased `CO_(2)` concentration in mesophyll cell
C. Spatial differentiation between `O_(2)` & RuBisCO
D. Greater affinity of RuBisCO for `CO_(2)`

Answer

**Step-by-Step Solution:**

1. **Understanding Photorespiration**:
- Photorespiration is a process that occurs in plants where the enzyme RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase) can fix oxygen instead of carbon dioxide, leading to a loss of energy and carbon.

2. **C4 Plants Overview**:
- C4 plants have a unique photosynthetic pathway that helps them minimize photorespiration. They are adapted to high light intensities, high temperatures, and low carbon dioxide concentrations.

3. **Mechanism in C4 Plants**:
- In C4 plants, carbon dioxide is initially fixed in mesophyll cells into a four-carbon compound (C4 acid), such as oxaloacetate.
- This C4 acid is then transported to bundle sheath cells, where it is converted back into carbon dioxide.

4. **Increased CO2 Concentration**:
- The breakdown of C4 acids in bundle sheath cells releases carbon dioxide, which increases the concentration of carbon dioxide around RuBisCO.
- This high concentration of carbon dioxide ensures that RuBisCO primarily acts as a carboxylase (fixing carbon dioxide) rather than an oxygenase (fixing oxygen).

5. **Minimizing Photorespiration**:
- Because of the increased concentration of carbon dioxide in the bundle sheath cells, the likelihood of RuBisCO engaging in photorespiration is significantly reduced.
- This adaptation allows C4 plants to maintain efficient photosynthesis even under conditions that would typically favor photorespiration in C3 plants.

6. **Conclusion**:
- Therefore, the reason there is no photorespiration in C4 plants is primarily due to the increased concentration of carbon dioxide in mesophyll cells, which ensures that RuBisCO functions effectively as a carboxylase.

**Final Answer**: In C4 plants, there is no photorespiration because of the increased carbon dioxide concentration in mesophyll cells.

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