The process which makes major difference between `C_(3)` and `C_(4)` plants is

Options

A. Glycolysis
B. Calvin cycle
C. Photorespiration
D. Respiration

Answer

To answer the question regarding the major process that differentiates C3 and C4 plants, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding C3 and C4 Plants**:
- C3 plants utilize the Calvin cycle for photosynthesis and primarily fix carbon dioxide into a three-carbon compound (3-phosphoglycerate).
- C4 plants, on the other hand, have a different mechanism where they first fix carbon dioxide into a four-carbon compound (oxaloacetate) before entering the Calvin cycle.

2. **Identifying Key Processes**:
- The question provides four processes: glycolysis, Calvin cycle, photorespiration, and respiration.
- Glycolysis is a metabolic pathway that occurs in all living cells, including both C3 and C4 plants, and is not specific to photosynthesis.
- The Calvin cycle is also present in both C3 and C4 plants, so it cannot be the distinguishing factor.

3. **Analyzing Photorespiration**:
- Photorespiration is a process that occurs in C3 plants when oxygen competes with carbon dioxide for the active site of the enzyme RuBisCO, leading to a wasteful pathway that reduces the efficiency of photosynthesis.
- C4 plants have evolved mechanisms to minimize photorespiration by spatially separating the initial carbon fixation from the Calvin cycle, effectively reducing the oxygenation reaction.

4. **Conclusion**:
- The major difference between C3 and C4 plants lies in the occurrence of photorespiration. C3 plants undergo photorespiration, while C4 plants have adaptations that significantly reduce or eliminate this process.
- Therefore, the correct answer to the question is **photorespiration**.

### Final Answer:
The process which makes a major difference between C3 and C4 plants is **photorespiration**.

---