Select the statement that is not correct from the following.

Options

A. Plants which utilizes first , RuBP in `CO_2` fixations are called `C_3` plants.
B. Plants which utilizes first , PEP in `CO_2` fixations are called `C_2` plants.
C. CAM plants lack structural compartmentalization of leaf , as found in `C_4` plants .
D. `C_4` photosynthetic pathway is more efficient than the `C_3` pathway.

Answer

To solve the question of selecting the statement that is not correct, we will analyze each of the statements provided.

### Step-by-Step Solution:

1. **Identify the Statements**: We need to review the statements provided in the question. The statements relate to types of plants based on their CO2 fixation pathways.

2. **Evaluate the First Statement**:
- "Plants which utilize RUBP in CO2 fixation are called C3 plants."
- This statement is correct. C3 plants use Ribulose 1,5-Bisphosphate (RUBP) in the Calvin cycle for CO2 fixation, producing 3-phosphoglycerate.

3. **Evaluate the Second Statement**:
- "Plants which use PEP in CO2 fixation are called C2 plants."
- This statement is incorrect. Plants that utilize Phosphoenolpyruvate (PEP) for CO2 fixation are known as C4 plants, not C2 plants. C2 plants are not a recognized category in photosynthesis.

4. **Evaluate the Third Statement**:
- "PAM plants lack structural compartmentalization of leaf as found in C4 plants."
- This statement is correct. PAM (photosynthetic assimilation of malate) plants do not have the same structural adaptations as C4 plants.

5. **Evaluate the Fourth Statement**:
- "C4 photosynthetic pathway is more efficient than the C3 pathway."
- This statement is also correct. The C4 pathway is more efficient under conditions of high light intensity and temperature because it minimizes photorespiration.

6. **Conclusion**:
- The second statement is the one that is not correct. Therefore, the answer to the question is that the statement about PEP being associated with C2 plants is incorrect.

### Final Answer:
The statement that is not correct is: "Plants which use PEP in CO2 fixation are called C2 plants."