Guard cells differ from other epidermal cells in having

Options

A. Large vacuoles
B. Secondary walls
C. Chloroplast with PEP -carboxylase enzyme
D. Absence of mitochondria

Answer

### Step-by-Step Solution

1. **Understanding Guard Cells**: Guard cells are specialized cells located in the epidermis of plant leaves and stems. They play a crucial role in regulating gas exchange and transpiration by controlling the opening and closing of stomata.

2. **Analyzing the Options**:
- **Option 1: Large Vacuoles**: While guard cells do contain vacuoles, this characteristic is not unique to them as many other epidermal cells also have vacuoles. Therefore, this option is incorrect.

- **Option 2: Secondary Walls**: Guard cells do not have secondary walls. Secondary walls are typically found in certain types of cells for structural support, but guard cells are not among them. Thus, this option is also incorrect.

- **Option 3: Chloroplasts with PEP Carboxylase Enzyme**: This option is correct. Guard cells contain chloroplasts, which are not found in most other epidermal cells. The presence of chloroplasts allows guard cells to perform photosynthesis and produce the energy needed for their function, particularly the opening and closing of stomata. The enzyme PEP carboxylase is involved in the process of photosynthesis and is crucial for the functioning of guard cells.

- **Option 4: Absence of Mitochondria**: This option is incorrect as guard cells do contain mitochondria, which are essential for energy production.

3. **Conclusion**: The unique feature of guard cells compared to other epidermal cells is the presence of chloroplasts, which contain the PEP carboxylase enzyme.

### Final Answer
Guard cells differ from other epidermal cells in having **chloroplasts with PEP carboxylase enzyme**.

---