The first carbon fixation in `C_(4)` pathway occurs in chloroplasts of

Options

A. guard cells
B. mesophyll
C. bundle sheath
D. all of these

Answer

To answer the question regarding where the first carbon fixation in the C4 pathway occurs, we can break down the solution step by step:

### Step-by-Step Solution:

1. **Understanding the C4 Pathway**: The C4 pathway is a photosynthetic process that involves the fixation of carbon dioxide into a four-carbon compound. This pathway is an adaptation to minimize photorespiration, especially in hot and dry conditions.

2. **Identifying the Key Cells**: In the C4 pathway, two main types of cells are involved: mesophyll cells and bundle sheath cells. Each of these cells plays a distinct role in the process of photosynthesis.

3. **Role of Mesophyll Cells**: The first step of carbon fixation in the C4 pathway occurs in the mesophyll cells. Here, carbon dioxide is fixed by a three-carbon compound called phosphoenolpyruvate (PEP) to form oxaloacetic acid, which is a four-carbon compound.

4. **Role of Bundle Sheath Cells**: After the initial fixation in the mesophyll cells, the four-carbon compound is then transported to the bundle sheath cells, where it undergoes further processing in the C3 cycle (Calvin cycle).

5. **Conclusion**: Based on the information gathered, the first carbon fixation in the C4 pathway occurs specifically in the chloroplasts of the mesophyll cells.

### Final Answer:
The first carbon fixation in the C4 pathway occurs in the chloroplasts of **mesophyll cells**.

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