In which of the following `CO_2` fixation and Calvin cycle are separated in time

Options

A. `C_4` plants
B. `C_3` plants
C. CAM plants
D. All the above

Answer

To answer the question regarding which type of plants exhibit temporal separation between CO2 fixation and the Calvin cycle, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding CO2 Fixation and the Calvin Cycle**:
- CO2 fixation refers to the process where carbon dioxide is incorporated into organic molecules. This occurs in the initial steps of photosynthesis.
- The Calvin cycle is the series of biochemical reactions that occur in the stroma of chloroplasts in photosynthetic organisms, where CO2 is converted into glucose.

2. **Identifying Plant Types**:
- There are three main types of plants based on their photosynthetic pathways: C3, C4, and CAM (Crassulacean Acid Metabolism) plants.

3. **Analyzing CAM Plants**:
- CAM plants open their stomata at night (scotoactive stomata) to minimize water loss. During this time, they fix CO2 into organic acids (like malate).
- During the day, when the stomata are closed, the fixed CO2 is released from these acids and enters the Calvin cycle to produce sugars.

4. **Analyzing C4 Plants**:
- C4 plants have a spatial separation of CO2 fixation and the Calvin cycle. CO2 is fixed in mesophyll cells, and the Calvin cycle occurs in bundle sheath cells, but both processes happen simultaneously.

5. **Analyzing C3 Plants**:
- C3 plants do not have any separation; both CO2 fixation and the Calvin cycle occur in the same location and at the same time.

6. **Conclusion**:
- Since CAM plants have a clear temporal separation between CO2 fixation (at night) and the Calvin cycle (during the day), they are the correct answer to the question.

### Final Answer:
The correct answer is **CAM plants**, as they exhibit temporal separation between CO2 fixation and the Calvin cycle.

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