In the `C_4` cycle, the 4 carbon - containing acids are formed in

Options

A. Mesophyll cells of maize leaf.
B. Mesophyll cells of cactus leaf.
C. Mesophyll cells of tomato leaf.
D. Mesophyll cells of banana leaf.

Answer

To solve the question about where 4-carbon containing acids are formed in the C4 cycle, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the C4 Cycle**:
- The C4 cycle is a photosynthetic pathway that allows certain plants to efficiently fix carbon dioxide (CO2) in conditions where it might otherwise be limited.

2. **Identifying C4 Plants**:
- C4 plants, such as maize (corn), have specialized structures that allow them to perform the C4 cycle. Other examples include sugarcane and sorghum.

3. **Location of 4-Carbon Acid Formation**:
- In C4 plants, the initial fixation of CO2 occurs in the mesophyll cells. Here, CO2 is combined with phosphoenolpyruvate (PEP) to form a 4-carbon compound, typically oxaloacetate, which is then converted into malate or aspartate.

4. **Role of Enzymes**:
- The enzyme PEP carboxylase plays a crucial role in this process by catalyzing the reaction that fixes CO2 into a 4-carbon compound.

5. **Transport to Bundle Sheath Cells**:
- The 4-carbon acids formed in the mesophyll cells are then transported to the bundle sheath cells, where they are decarboxylated to release CO2 for use in the Calvin cycle.

6. **Analyzing the Options**:
- The options provided are:
- Mesophyll cells of maize leaf
- Mesophyll cells of cactus leaf
- Mesophyll cells of tomato leaf
- Mesophyll cells of banana leaf
- Since maize is a known C4 plant, the correct answer is the mesophyll cells of maize leaf.

7. **Excluding Incorrect Options**:
- Cactus is a CAM (Crassulacean Acid Metabolism) plant, not a C4 plant.
- Tomato and banana are C3 plants, which do not utilize the C4 cycle.

### Final Answer:
The 4-carbon containing acids are formed in the **mesophyll cells of maize leaf**.