How do you conduct the onion peel skin experiment?

The onion peel skin experiment allows students to view real plants cells under a microscope. This experiment is conducted by firstly peeling a small section of the thin membrane from a piece of onion. This piece of membrane will then be placed on a microscope with a drop of water to prevent the cells drying out, followed by the addition of Iodine solution which will stain the cells to make them visible. A thin glass slip will then be added, and once these steps have all been completed the students will be able to view the cells under a microscope.

As mentioned above, in the reply from Paula, the process is straightforward. Her method works well. In an examination question, it is worth adding the following 2 points :

1. lowering the coverslip with a mounted needle will force any air bubbles out and make for a clearer image.
2. adding a stain, such as iodine, allows you to see individual structures by enhancing the CONTRAST between the different tissues present in the sample.

1. Firstly, peel a thin layer of the transparent epidermal to gather cells from inside the onion.
2. Then, carefully place this layer on a microscopic slide.
3. Add a drop of iodine in order to stain the cells to be more visible.
4. Finally, place a coverslip onto the onion cells using forceps, carefully done to avoid air bubbles from occurring.

• Use tweezers to peel off a thin layer of the onion skin.
• Careful place the skin on a glass slide and lay it out flat (be careful to avoid folds).
• Add a drop of iodine solution to stain the cells (this will make it easier to see).
• Place a cover slip (thin glass square) over the skin slowly by standing it up on one side and lowering it carefully until it is flat (this is to avoid air bubbles forming).
• Place the prepared slide on the stage of your microscope and secure in place with the clips.
• Make sure the main lens (objective lens) is on the smallest number (lowest magnification).
• Look through the eye piece and turn the rough focusing wheel/dial until you can clearly see the sample (cells may appear very small at this stage).

From now you can use the fine focusing wheel to focus more precisely and increase the magnification by changing the objective lens to a higher number as required. You may need to re-focus with the fine focusing wheel when you do this.

Peel off a leaf from half a piece of onion and using the forceps, pull out a piece of transparent onion peel (epidermis) from the leaf. Put the epidermis in the watch glass containing distilled water. Take a few drops of safranin solution in a dropper and transfer this into another watch glass.

Here's how to conduct the onion peel skin experiment in a few steps:

1. First, add a few drops of water or solution to the microscope slide to avoid dryness and wilting
2. Take a small piece of onion and using tweezers, peel off the membrane from the underside (the rough side).
3. Place the membrane flat on the surface of the slide.
4. Add a drop of Iodine solution to the onion skin
5. Using a pin, lower the thin glass coverslip or cover glass onto the slide. Make sure there are no air bubbles
6. Make sure the lowest power objective lens is in line with the optical tube, and the microscope light is turned on. Then place the prepared slide onto the stage of the microscope.
7. Looking from the side lower the tube using the coarse focus knob until the end of the objective lens is just above the cover glass. Do this carefully so as not to crack the cover glass (and possibly damage the objective lens).
8. Now look through the eyepiece and turn ONLY the smaller, fine focusing knob to move the optical tube upwards until an image comes into focus. The cells should look something like lizard skin.
9. Swap the objective lens for a higher powered one so that you can see the cells at greater magnification. You should be able to make out a nucleus in each cell.
10. Be very careful; these dyes can stain your skin and clothes. Could be dangerous if it is on you.

take a cutting that is 1 cell thin dye with methly-blue or iodine, place on glass slide with cover slip and use the microscope to look at the sample

When using onion skin to look at the cells under a microscope, the first thing you need to cut a small sample of onion using a scalpel. After this separate, the sections of onion and with tweezers remove a thin layer of onion skin. Place the onion skin onto a microscope slide and place 2 drops of iodine solutions (stain) on the onion skin (this allows you to see the cells). Carefully lower a cover slip on the sample. Place the slide on the base of the microscope and start on the lowest magnification (widest view). Focus until cells are found and then move up to the next objective lens.

I would help her by peeling the skin of onion and disected part would be examined by the help of compound microscope

This is a great experiment to view plant cells and practice your specimen staining skills. Firstly, you need to get together your materials:

• forceps
• Onion
• microscope
• Slide
• Iodine solution
• coverslip

Start by taking a small section of onion and peel off a thin layer of skin using forceps. Lie the tissue flat on the slide and add a drop of iodine solution. Slowly place on the coverslip to avoid air bubbles. Place the slide underneath the microscope at the objective lens and slowly work up to a higher objective lens by focusing using the course and fine focus.

Carefully cut an onion into sections using a sharp knife or scalpel. Place a drop or two of Iodine solution onto a clean microscope slide. Using tweezers, remove the thin layer of skin from the underside of the onion, taking care not to twist or fold it. Place it on the Iodine solution. Hold a cover slip at an angle less than 90 degrees to the slide, in the Iodine solution, and allow it to meet the slide. In this way you will have hopefully removed any air bubbles and under the microscope will be able to clearly see the cell walls that have been stained brown.

Presence of large vacuoles and cell wall confirms that cells of onion peel are plant cells. Take a piece of onion and bend it to remove the transparent membranous structure called onion epidermal peel.

1. Use a dropping pipette to put one drop of water onto a microscope slide.

2. Peel off a thin layer of epidermal tissue from the inner surface.

3. Use forceps to put this thin layer on to the drop of water that you have placed on the microscope slide.

4. Put two drops of iodine solution onto the onion tissue.

5. Carefully lower a coverslip onto the slide. Do this by:

• placing one edge of the coverslip on the slide

• use the forceps to lower the other edge onto the slide

6. Put the slide on the microscope stage.

Peel one layer of the onion skin and place the the skin on a microscope slide. Then, put a drop of iodine on the onion skin and place the slide under a microscope. Set the microscope to the lowest magnification and observe the cell structure. You should be able to see the nucleus of the cell.

This is the method for the GCSE Biology required practical:

1. Safety first - make sure that you put safety goggles on and tie long hair back. If you have a lab coat, put it on. Make sure you remain standing throughout the practical. Remember, iodine is an irritant and can stain clothing, so be careful when handling it. Also, treat glass with care to prevent breakage.
2. Gather your equipment. You will need:
3. Light microscope
4. Slide
5. Cover slip
6. Distilled water
7. Onion
8. Tweezers
9. Iodine
10. Add a drop of distilled water to the centre of the slide.
11. Use the tweezers to peel off the epidermis (skin) from underneath a layer of onion, then place it onto the drop of distilled water, making sure that it is as flat as possible.
12. Add a drop of iodine to the top of the onion epidermis.
13. Carefully lower the cover slip onto the sample of onion skin, lowering it gradually from one side to the other to make sure no air bubbles get trapped.
14. Place the prepared slide on the stage of the microscope and ensure that it is centred under the objective lens.
15. View the sample using the lowest magnification of objective lens first, and adjust the light source to the appropriate brightness before focussing the objective lens using the course focus being careful not to touch the slide with the lens.
16. Use the fine focus knob to bring the image into clear focus. You may now wish to observe the sample under higher magnifications by increasing the objective lens magnification.