In `C_(4)` plants , initial `CO_(2)` fixation takes place in the chloroplasts of

Options

A. (a) Guard cells
B. (b) Mesophyll cells
C. (c) Spongy tissue
D. (d) Bundle sheath

Answer

**Step-by-Step Solution:**

1. **Understanding C4 Plants**: C4 plants utilize a specific pathway for photosynthesis known as the C4 pathway or the Hatch-Slack pathway. This pathway is more efficient than the C3 pathway due to its ability to minimize photorespiration.

2. **Location of Initial CO2 Fixation**: In C4 plants, the initial fixation of carbon dioxide occurs in the chloroplasts of mesophyll cells. This is the first step in the C4 pathway.

3. **Process of CO2 Fixation**: The enzyme PEP carboxylase catalyzes the reaction in which carbon dioxide is fixed to phosphoenolpyruvate (PEP) to form a four-carbon compound called oxaloacetic acid (OAA) in the mesophyll cells.

4. **Further Processing**: The oxaloacetic acid is then converted into malate or aspartate and transported to the bundle sheath cells, where it is converted back to carbon dioxide and enters the Calvin cycle (C3 cycle) for further processing.

5. **Conclusion**: Since the question specifically asks about the initial fixation of CO2, the correct answer is that it takes place in the chloroplasts of mesophyll cells.

**Final Answer**: The initial CO2 fixation in C4 plants takes place in the chloroplasts of **mesophyll cells**.

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