PEP is primary `CO_(2)` acceptor in

Options

A. `C_(4)` plants
B. `C_(3)` plants
C. `C_(2)` plants
D. both `C_(3)` and `C_(4)` plants.

Explanation

To answer the question "PEP is the primary CO₂ acceptor in," we will analyze the role of PEP (phosphoenolpyruvate) in different types of plants, specifically C3 and C4 plants.

### Step-by-Step Solution:

1. **Understanding PEP**:
- PEP stands for phosphoenolpyruvate, which is a three-carbon compound involved in the process of photosynthesis.
- It acts as a primary carbon dioxide (CO₂) acceptor during the initial stages of carbon fixation.

2. **C4 Plants**:
- In C4 plants, the process of photosynthesis begins with the carboxylation of PEP.
- The enzyme responsible for this reaction is called PEP carboxylase, which is highly expressed in the mesophyll cells of C4 plants.
- When CO₂ is fixed, PEP combines with CO₂ to form oxaloacetic acid (OAA), a four-carbon compound.

3. **C3 Plants**:
- In C3 plants, the primary CO₂ acceptor is ribulose bisphosphate (RuBP), not PEP.
- Therefore, PEP is not the primary CO₂ acceptor in C3 plants.

4. **C2 Plants**:
- C2 plants, also known as photorespiratory plants, do not primarily utilize PEP for CO₂ fixation. Instead, they have a different mechanism that does not involve PEP as a primary acceptor.

5. **Conclusion**:
- Based on the above analysis, PEP is the primary CO₂ acceptor specifically in C4 plants.

### Final Answer:
PEP is the primary CO₂ acceptor in **C4 plants**.