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The epidermal cells of onions provide a protective layer against viruses and fungi that may harm the sensitive tissues. Because of their simple structure and transparency they are often used to introduce students to plant anatomy[1] or to demonstrate plasmolysis.[2] The clear epidermal cells exist in a single layer and do not contain chloroplasts, because the onion fruiting body (bulb) is used for storing energy, not photosynthesis.[3] Each plant cell has a cell wall, cell membrane, cytoplasm, nucleus, and a large vacuole. The nucleus is present at the periphery of the cytoplasm. The vacuole is prominent and present at the center of the cell, surrounded by cytoplasm.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/1/1a/Cells_from_a_red_onion_epidermal_peel.tif/lossy-page1-220px-Cells_from_a_red_onion_epidermal_peel.tif.jpg)
Firm, small onions are best for microscopy. The epidermal layers are removed by cutting the onion and peeling them off (they are the membrane-like sheaths between each onion layer). For advanced microscopy, such as fluorescence microscopy, the layers halfway between the outside and the centre of the onion are best.
References
edit- ^ "Plant anatomy at the University of Hamburg". Biologie.uni-hamburg.de. Archived from the original on 2013-01-22. Retrieved 2012-09-29.
- ^ Samworth, Mike. "Plasmolysis". Microscopy-uk.org.uk.
- ^ "Onion and Cheek Cells".