`C_(4)` plants are more efficient in photosynthesis than `C_(3)` plants due to

Options

A. Lowest rate of photorespiration
B. Higher leaf area
C. Presence of larger number of chloroplasts in the leaf cells
D. Presesnce of thin cuticle

Answer

**Step-by-Step Solution:**

1. **Understanding C3 and C4 Plants:**
- C3 plants utilize the Calvin cycle for photosynthesis, where the enzyme RuBisCO fixes carbon dioxide directly to ribulose bisphosphate (RuBP).
- C4 plants, on the other hand, have a different mechanism that involves an additional step before the Calvin cycle, allowing them to efficiently fix carbon dioxide.

2. **Photorespiration in C3 Plants:**
- In C3 plants, RuBisCO can also bind to oxygen instead of carbon dioxide, especially under conditions of high oxygen concentration and low carbon dioxide concentration. This leads to a process called photorespiration, which is wasteful as it does not produce sugars or ATP.

3. **C4 Photosynthesis Mechanism:**
- C4 plants have specialized anatomy known as Kranz anatomy, which includes two types of cells: mesophyll cells and bundle sheath cells.
- In mesophyll cells, carbon dioxide is initially fixed into a four-carbon compound (oxaloacetate) and then converted to malate or aspartate, which is transported to bundle sheath cells.

4. **Reduction of Photorespiration:**
- In the bundle sheath cells, malate is decarboxylated to release carbon dioxide, which is then used by RuBisCO. This increases the concentration of carbon dioxide around RuBisCO, minimizing the chances of it binding to oxygen.
- As a result, C4 plants experience significantly lower rates of photorespiration compared to C3 plants.

5. **Conclusion:**
- Due to the reduced rate of photorespiration, C4 plants are more efficient in photosynthesis, particularly in hot and dry environments where C3 plants would suffer more from photorespiration.

**Final Answer:**
C4 plants are more efficient in photosynthesis than C3 plants due to their lower rate of photorespiration, which is facilitated by their unique Kranz anatomy and the ability to concentrate carbon dioxide around the enzyme RuBisCO.

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