The epidermis of an onion scale leaf should include both the inner and outer epidermis, neither of which has chloroplasts.

The difference is that the outer epidermal cell vesicles may be purple, so it is often used to do the plasma wall separation and recovery experiments (purple and colorless contrast); the inner epidermal cells are colorless, so it can be stained with the appropriate stains to observe the various organelles, or the distribution of DNA, RNA, or fat distribution.

Picture of a clinical slide of epidermal cells from an onion scale leaf

Extended information

Steps for making a clinical slide of inner epidermal cells from an onion scale leaf

Wipe the slide and coverslip, gently hold the edges of the slide between the forefinger and thumb in one hand, and take the gauze with the other hand to put the slide between the two layers of gauze. Gently wipe the slide by holding it between the index finger and thumb with even pressure.

2. Use the eyedropper to drop a drop of water in the center of the slide, with the appropriate amount of the best, too small a drop of water is easy to produce bubbles or dry, affecting the observation, too large a drop of water is easy to overflow the slide and contaminate the microscope.

3. Tear the film on the surface of the onion bulb with tweezers, to 0.5cm × 0.5cm is appropriate. The same as the previous step, emphasize the appropriate amount, put the torn film in the drop of water in the center of the slide, and use tweezers to spread it carefully, the larger the torn film will be less likely to spread.

4. Cover the coverslip with the aim of preventing air bubbles from appearing under the coverslip.

5. Place the made mount on the microscope objective stage, so that the experimental material under the coverslip is located in the center of the light-through hole, focusing observation, this step should pay attention to: a. Observe with a low magnification. b. Strictly in accordance with the operating procedures of the microscope to be carried out. (6) Staining, remove the mount from the microscope carrier stage and place it on the table for staining. Students should be told here that staining should not be done directly on the microscope's carrier stage, otherwise the microscope will be contaminated, and the stained mount must be wiped clean of the surrounding liquid before observing it with the microscope.

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