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A dandelion is a short plant, usually with a yellow flower head and notched leaves. A dandelion flower head consists of many tiny flowers. The dandelion is native to Europe and Asia, and has spread to many other places. The dandelion is also known by its generic name Taraxacum. In Northern areas and places where the dandelion is not native, it reproduces asexually.
Detailed Description
The Dandelion Clock The flower matures into a globe of fine filaments that are usually distributed by wind, carrying away the seed-containing achenes. This globe (receptacle) is called the "dandelion clock", and blowing it apart is a popular pastime for children. In German it's called a Pusteblume, translated as "blow flower". The number of blows required to completely rid the clock of its seeds is deemed to be the time of day. The Seeds The flower head is surrounded by bracts (sometimes mistakenly called sepals) in two series. The inner bracts are erect until the seeds mature, then flex down to allow the seeds to disperse; the outer bracts are always reflexed downward. Some species drop the "parachute" (called a pappus, modified sepals) from the achenes. Between the pappus and the achene, there is a stalk called beak, which elongates as the fruit matures. The beak breaks off from the achene quite easily. Name The name dandelion is derived from the Old French, dent-de-lion, which is literally "lion's tooth", referring to the sharply-lobed leaves of the plant. The English spelling reflects the French pronunciation at the time this French word was absorbed into English. The first written usage of the word occurs in an "herbal" dated 1373, but there is a 1363 document in which the word "dandelion" was used as a proper name (Willelmus Dawndelyon). In German, the dandelion is called Löwenzahn, which is also translated as "lion's tooth." In modern French the plant is called pissenlit, which means "urinate in bed", apparently referring to its diuretic properties. Likewise, "pissabeds" is an English folkname for this plant, and "piscialletto" is one of its folknames in Italian (with "dente di leone", meaning "lion's tooth"). Similarly in Spanish, it is known as the "meacamas", but also commonly "diente de león". Selected species Seed developement and genetics As aforementioned, the taxonomical situation of the genus is quite complex, mainly because many dandelions are genetically triploid. An odd number of chromosomes usually is associated with sterility, but dandelions with this karyotype can reproduce without fertilization, a process called apomixis. In these individuals flowers are useless vestigial structures, although they may still produce a small percentage of fertile pollen, keeping some genetic contact with sexual individuals. Diploid dandelions develop seeds after cross-pollination and are self-incompatible. In most zones of southern Europe and Asia, dandelion populations are sexual or mixed sexual-apomictic, while in northern coutries only triploid and tetraploid apomicts are present, as is in the zones where it is not native. This seems to be linked to higher temperatures, survival of pre-glacial populations and human impact, but the subject is still being studied. There are usually 54 to 172 seeds produced per head, but a single plant can produce more than 2000 seeds a year. It has been estimated that more than 97 000 000 seeds/hectare could be produced every year by a dense stand of dandelions. Uses
Antioxidant Properties of Dandelion Dandelion contains Luteolin, an antioxidant, and has demonstrated antioxidant properties without cytotoxicity. Chun Hu and David D. Kitts. Food, Nutrition and Health, Faculty of Agricultural Sciences, University of British Columbia, Vancouver, BC, Canada. October 2004. Luteolin and luteolin-7-O-glucoside from dandelion flower suppress iNOS and COX-2 in RAW264.7 cells. Springer Netherlands. 245:1-2(107-113). * Caffeic Acid and Carcinogenicity Caffeic acid is a secondary plant metabolite produced in dandelion, yarrow, horsetail and whitethorn. Despite its name, it is totally unrelated to caffeine. Recent studies have revealed this acid may be carcinogenic. Caffeic acid was tested for carcinogenicity by oral administration in mice, it produced renal cell adenomas in females, and a high incidence of renal tubular cell hyperplasia in animals of each sex. False Dandelions Dandelions are so similar to catsears (Hypochoeris) that catsears are also known as "false dandelions". Both plants carry similar flowers which form into windborne seeds. However, catsear flowering stems are forked and solid, whereas dandelions possess unforked stems that are hollow. Both plants have a rosette of leaves and a central taproot. However, the leaves of dandelions are jagged in appearance, whereas those of catsear are more lobe-shaped and hairy. Other plants with similar flowers include hawkweeds (Hieracium) and hawksbeards (Crepis). These are both readily distinguished by their branched flowering stems. See also | |||||||||||||
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