Plant of the month (©Pierre Laszlo, all rights reserved)
Daucus carota (Apiaceae)
Who said veggies are a dull topic ? Carrots are so common as to seem uninteresting, but are among the top ten vegetable crops globally in term of area of production and market value.
Moreover, this vegetable offers quite a few queries, for instance why is carotene orange in color? Does it occur also in the citrus fruit of that name? If so, why such a conjunction? How did mankind domesticate this plant, and where did it originate? What are its relatives?
Carrots are native to Afghanistan, their domestication began there about 1100 years ago. They then spread to Europe through the Middle-East. The Spanish name zanahoura, originating in Andalus Arabic, is a reminder of that route. From Europe, they emigrated to the Americas.
The common name of the wild plant in English, Queen Anne’s lace — refers to the umbel of tiny white flowers, ‟a pious wish to whiteness gone over‟, as wrote in a poem William Carlos Williams. Queen Anne was the British monarch from 1702 until her death in 1714. As for the word carrot, it comes via the Latin and Greek languages from an Indo-European root –ker, with the meaning of a horn, referring to the shape of the tap root.
Other plants from the same family of the Apiaceae include celery. Carrots can also occur in a variety of colors : white, yellow, light orange, orange, dark orange, red or even purple. These are dictated by a combination of genes and modifier genes acting in the xylem — the vascular tissue, akin to wood, inside the carrot root.
The relatively small genome of 155,911 base pairs was determined in 2006. Since carrots are easily stored and are biennial, they are amenable to genetic engineering. Foreign genes can be inserted for oral delivery of vaccines and other proteins with therapeutic value. But will such ‟improvements‟ prove acceptable to public opinion ?
The pigments are alpha and beta carotene (orange), lycopene in addition to the carotenes (dark orange) , xantophylls (yellow), anthocyanins (yellow and red). The carotenes (absent from Queen Anne’s lace), are a major reason for the nutritive value of carrots. They provide about 30 % of the provitamin A (precursor to vitamin A) consumed in the United States. Vitamin A has multiple functions: it is important for growth and development, for the maintenance of the immune system and good vision.
Vitamin A is needed by the retina of the eye in the form of retinal, a small molecule of the aldehyde group which combines with the protein opsin to form rhodopsin, the light-absorbing molecule that is necessary for both low-light and color visions. During World War II, the British circulated the disinformation, even though it was true, that RAF pilots were given a diet high in carrots, to enhance their night vision. It was mostly a smokescreen to hide the successful use of radar by the British to detect enemy planes.
These main pigments of the carrot, aptly named carotenes, owe their orange color to their molecules holding a fluid of electrons tuned to withdraw from visible light other radiations than orange — hence they appear orange. They are antioxidants — another nutritional plus. Carotenes, widespread pigments in plants, also occur in the skin of citrus fruit.
Mothers are very inventive, coming up with many other arguments to make toddlers eat their carrots.