Absence of which of the following process marks a major difference `C_(3) and C_(4)` plants is

Options

A. glycolysis
B. Calvin cycle
C. Photorespiration
D. respiration

Explanation

To answer the question regarding the major difference between C3 and C4 plants, we can follow these steps:

### Step-by-Step Solution:

1. **Understand C3 and C4 Plants**:
- C3 plants utilize the Calvin cycle (C3 cycle) for carbon fixation.
- C4 plants have a specialized mechanism that includes an additional cycle (C4 cycle) for carbon fixation, which helps them efficiently capture carbon dioxide.

2. **Identify Key Processes**:
- Both C3 and C4 plants undergo the Calvin cycle.
- Glycolysis and respiration are processes that occur in both types of plants.

3. **Focus on Photorespiration**:
- Photorespiration is a process that occurs in C3 plants when the enzyme RuBisCO reacts with oxygen instead of carbon dioxide, especially under conditions of high oxygen concentration.
- This process is wasteful as it does not produce energy or sugars.

4. **C4 Plants and Photorespiration**:
- In C4 plants, the structure (Kranz anatomy) and biochemical pathway prevent photorespiration from occurring. They maintain a higher concentration of carbon dioxide at the site of RuBisCO, thus reducing the likelihood of oxygen binding.

5. **Conclusion**:
- The absence of photorespiration is the major difference between C3 and C4 plants. While C3 plants experience photorespiration, C4 plants do not, which allows them to be more efficient in photosynthesis, particularly in hot and dry environments.

### Final Answer:
The absence of **photorespiration** marks a major difference between C3 and C4 plants.

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