WHO INVENTED THE
"ONION SKIN" BIOLOGY LAB?
Walter Dioni - Cancún, México
In Uruguay 70 years ago the epidermis of the inner side of the scales of the onion bulb was the model used to teach me the configuration of a cell, and I always imagined that it would be reported from years before, on a global scale (in reality, "globally", taking into account the scientific background of those years would mean (in alphabetical order): England, France, Germany, United States).
I made a long review (and a much delayed one!) through "search engines" and in the older texts of Botany, as well as the “Manuals for laboratory practices in Botany”, published on the Internet Archive. I am not complaining. I could see, and I really enjoyed the amazing skill of the artists, who filled those old books with unbelievably beautiful images of plants and its parts, that rival (and many times are better, if we discard the color) many current photos.
Also in 1887, in the English translation of Strasburger’s "Microscopic Botany", (pag 29, fig 15) the now classical onion only contributes with its roots to the education of botanists. In 1889, Ch.E. Bessey in his “Botany”, uses Fritillaria (p. 3, fig 2) and Tradescantia (p. 12, fig.7) cells in some discussions. In his edition of 1896 of the same text, although citing the onion 7 times he is only interested in the root.
Apparently his books had not much success!
One portion of a Tradescantia (Rhoeo) spatifolia, staminal hair. DC3 Motic Cámera
One cell from a staminal hair of Tradescantia (Rhoeo) spatifolia, stained with eosin, from my work on “Eosin as a nuclear stain”
Three marvelous pictures of a Tradescantia staminal hair taken though his DIC microscope, were published by Franz Neidl in:
Another beautiful rendition of this subject is the one by Phil Gates in his blog:
Invented by Georges Nomarski in 1950 the DIC microscope has revolutionized the photomicrography, and become with justice the favorite of now many microscopists.
Interestingly a practical histology handbook mainly dedicated to animal and human histology, Outlines of practical histology, (2nd. ed.) W. Stirling, 1894, uses the "onion skin" as an example of epithelium (fig 57, page 103)
In 1900 Clements & Cutter in his austere "A laboratory manual of High School Botany" recommended cells of several different plants to display various aspects of the same, but never the onion cells. Innovatively, to display the cyclosis they recommended the hairs of the stem of young tomato plants (occasionally other authors recommend (then and now) the cells of the pulp of the fruit of tomato to display cells with coloured vacuoles, or the skin of the same fruit to show chromoplasts)
In 1921 J.E. Peabody, and A.E. Hunt, published their “Elementary biology, plant, animal, human”. At p. 27 delineate their Lab.Study No. 21, which recommended the use of onion skin (without the use of any colouring) to show the cell plant, and then the use of Elodea leaf, to see chloroplasts and the cyclosis. In a foot note we can appreciate the suggestion of "this wonderful material" by Mrs Elsie M. Kupfer, Head of the Department of Biology of the Wadleigh High School, New York City, what suffices alone to show that even at that time, 31 years after Bastin, the use of both materials was of little or no use. In 1922, it is recommended, in just 3 lines, the use of the onion skin in the book of A.G. Tansley, Elements of Plant biology, perhaps indicating a tendency to generalize their use in Anglophone schools.
A DIC image of the onion epidermis, by Steve Durr, was included in my “Homage to the onion skin” you can see it at this link:
This is a picture of the floral cradles of Tradescantia (Rhoeo) spatifolia- In the interior of the protective bracteae the little flowers reach maturity one after the other.
One mature flower of Tradescantia (Rhoeo), showing the stamens, with its famous staminal hairs. The flower is only 5 mm wide. Canon Powershot A300
Not for nothing do I record their use since the mid-18th century, one hundred and thirty-five years ago. The staminal hairs not only display all the structures of a typical plant cell, but additionally allows an easy exploration of the cyclosis which my onion cells show with difficulty, and even permit to watch mitosis in live, as these photos with a DIC microscope wonderfully display.
But "the tradescantias" are probably much more difficult to obtain and maintain, and even to use (the stamen hairs are very small items, and need to be picked from not fully developed minute flowers), especially for its use in schools at a worldwide range, compared to the humble, large, easy to manipulate and store, and always accessible onion.
Comments to the author,
, are welcomed.
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Published in the March 2011 edition of Micscape.
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