In land plants the guard cells differ from other epidermal cells in having:

Options

A. Chloroplasts
B. Cytoskeleton
C. Mitochondria
D. Endoplasmic reticulum

Answer

**Step-by-Step Solution:**

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

2. **Comparison with Other Epidermal Cells**: Unlike other epidermal cells, guard cells have unique characteristics that enable them to perform their specific functions.

3. **Identifying Key Differences**: The question asks for the specific difference between guard cells and other epidermal cells. The options provided are chloroplasts, cytoskeleton, mitochondria, and endoplasmic reticulum.

4. **Analyzing Chloroplasts**: Guard cells contain chloroplasts, which are organelles responsible for photosynthesis. Chloroplasts contain chlorophyll, the green pigment that captures light energy for photosynthesis. This is a significant difference because most other epidermal cells do not contain chloroplasts.

5. **Evaluating Other Options**:
- **Cytoskeleton**: Present in all cells, including both guard cells and other epidermal cells, to maintain cell shape. Thus, it is not a distinguishing feature.
- **Mitochondria**: Also present in all cells as the powerhouse of the cell, producing energy. This does not differentiate guard cells from other epidermal cells.
- **Endoplasmic Reticulum (ER)**: Present in all cells for protein and lipid synthesis. This is not a unique feature of guard cells.

6. **Conclusion**: The primary distinguishing feature of guard cells compared to other epidermal cells is the presence of chloroplasts.

**Final Answer**: Guard cells differ from other epidermal cells in having chloroplasts.

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