`CO_(2)` concentrating steps are found in
(a) `C_(3)` plants
(b) `C_(4)`plants
(c) CAM plants
(d) Temperate plants

Options

A. `C_(3)` plant
B. `C_(4)` plants
C. CAM plants
D. Temperate plants

Answer

To solve the question regarding where carbon dioxide concentrating steps are found, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Types of Plants**:
- Identify the types of plants mentioned in the options: C3 plants, C4 plants, CAM plants, and temperate plants.

2. **Define CO₂ Concentrating Mechanism**:
- Recognize that CO₂ concentrating mechanisms are processes that enhance the concentration of carbon dioxide for photosynthesis.

3. **Identify C4 Plants**:
- C4 plants are known for their unique photosynthetic pathway that includes a CO₂ concentrating mechanism. This is due to their specialized anatomy, known as Kranz anatomy.

4. **Explain Kranz Anatomy**:
- In C4 plants, the process involves two types of cells: mesophyll cells and bundle sheath cells. The mesophyll cells initially capture CO₂ and convert it into a four-carbon compound.

5. **Describe the C4 Pathway**:
- The CO₂ combines with phosphoenolpyruvate (PEP) in the mesophyll cells, catalyzed by the enzyme PEP carboxylase, forming oxaloacetic acid (OAA), which is then converted into malate.

6. **Malate Transport and Release**:
- The malate is transported to the bundle sheath cells, where it releases CO₂ and regenerates pyruvate, which is sent back to the mesophyll cells.

7. **Conclusion**:
- The released CO₂ then enters the Calvin cycle in the bundle sheath cells to produce sugars. Therefore, the CO₂ concentrating steps are primarily found in C4 plants.

### Final Answer:
The correct option is (b) C4 plants.

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