Stomatal apparatus consists of

Options

A. Guard cells only
B. Gurad cells + stomatal aperture only
C. Guard cells + stomatal aperture + subsidiary cells
D. Guard cells + stomatal aperture + subsidiary cells + vessel members

Answer

To answer the question "Stomatal apparatus consists of," we need to identify the components that make up the stomatal apparatus. Here's a step-by-step breakdown of the solution:

### Step-by-Step Solution:

1. **Identify the Main Components**:
- The stomatal apparatus primarily consists of guard cells, which are specialized cells that control the opening and closing of the stomata.

2. **Understand the Function of Guard Cells**:
- Guard cells are typically kidney-shaped and are responsible for regulating the size of the stomatal aperture. They do this by changing shape in response to the influx of potassium and sodium ions, which causes them to swell or shrink.

3. **Recognize the Stomatal Aperture**:
- The stomatal aperture is the opening that forms between the guard cells when they open. This aperture allows for gas exchange and transpiration (the loss of water vapor).

4. **Include Subsidiary Cells**:
- In addition to guard cells and the stomatal aperture, the stomatal apparatus also includes subsidiary cells. These are accessory cells that support the guard cells and help in their function. They can store essential nutrients and assist in the regulation of stomatal opening and closing.

5. **Evaluate the Options**:
- Now, let’s evaluate the provided options:
- **Option 1**: Guard cells only - Incomplete.
- **Option 2**: Guard cells in stomatal aperture only - Incomplete.
- **Option 3**: Guard cells, stomatal aperture, subsidiary cells - Complete.
- **Option 4**: Guard cells, stomatal aperture, subsidiary cells, and vessel membranes - Incorrect, as vessel membranes are not part of the stomatal apparatus.

6. **Conclusion**:
- The correct answer is **Option 3**: Guard cells, stomatal aperture, and subsidiary cells.

### Final Answer:
The stomatal apparatus consists of guard cells, stomatal aperture, and subsidiary cells.

---