Onion Skin Epidermal Cells: How to Prepare a Wet Mount Microscope Slide

Summary

This educational video demonstrates the process of preparing a wet mount slide of stained onion epidermal cells. The presenter explains how to select and peel the thin, transparent layer of cells from an onion bulb, transfer it onto a microscope slide, and apply iodine for staining. The video also covers techniques for placing a cover slip to minimize air bubbles and adjusting the microscope's light levels for optimal viewing. Finally, the presenter shows the cells magnified under different objective lenses, highlighting the cell walls, nuclei, and the importance of staining for visibility.

Takeaways

• 🔬 The video demonstrates how to prepare a wet mount slide of stained onion epidermal cells.
• 🧐 The process begins with selecting a smooth and shiny layer of onion bulb for obtaining the specimen.
• 🔎 A thin, transparent layer of cells is peeled off the onion layer using tweezers for use as the specimen.
• 📍 An alternate technique mentioned is peeling the onion skin directly onto the slide for a larger, flatter specimen.
• 💧 Iodine is used as the wet mount solution, which also serves to stain the cells for better visibility.
• 🏷️ A cover slip is applied by holding it at a right angle and allowing it to drop onto the slide, minimizing air bubbles.
• 🔭 The specimen is first examined under a 4X objective lens, magnifying the cells 40 times actual size.
• 🔍 The video explains that a compound microscope is parfocal, allowing for easy transition between different magnification levels.
• 🌑 Adjusting the light level by using the dimmer dial or iris diaphragm can improve contrast and visibility of the specimen.
• 🔬 The final examination is done under a high dry lens at 400 times actual size, revealing detailed cell structures.

Q & A

What is the purpose of the video?

The purpose of the video is to demonstrate the process of preparing a wet mount slide of stained onion epidermal cells.

What type of specimen is used in the video for the wet mount slide?

The specimen used is a thin, transparent layer of onion epidermal cells obtained from the inner layer of an onion bulb.

How does one identify the correct layer of onion epidermal cells?

The correct layer is identified by its smooth and shiny appearance compared to the rough and matte side of the onion layer.

What technique is shown for obtaining the onion epidermal cells?

The technique involves breaking the onion layer towards the shiny side and gently peeling apart the two pieces to obtain the thin layer of cells.

How should one handle the thin layer of onion epidermis to place it on the slide?

The thin layer should be torn off with tweezers and then carefully spread out on the slide to avoid it folding over on itself.

What alternative method is suggested for transferring the onion skin to the slide?

The alternative method is to peel the layer of onion skin directly onto the slide, allowing it to wrap around the slide like Saran Wrap.

What staining agent is used in the video for the wet mount?

Iodine is used as the staining agent, which provides both the wet component and stains the cells for better visibility.

How is a cover slip applied to the specimen on the slide?

The cover slip is held at a right angle to the slide and then dropped, allowing it to fall and push the air out, creating fewer air bubbles.

What magnification is used to initially examine the onion epidermal cells?

The initial examination uses a 4X objective lens, magnifying the specimen 40 times actual size.

How can the contrast of the specimen be improved if the stain is not taken up well?

The contrast can be improved by adjusting the light level, either by using the dimmer dial on the microscope base or by opening or closing the iris diaphragm.

What is the highest magnification used in the video to view the onion epidermal cells?

The highest magnification used is with the high dry power objective lens, which magnifies the specimen 400 times actual size.