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Lettuce (''Lactuca sativa'') is an annual plant of the daisy family Asteraceae. It is most often grown as a leaf vegetable, but sometimes for its stem and seeds. Lettuce was first cultivated by the ancient Egyptians who turned it from a weed, whose seeds were used to produce oil, into a food plant grown for its succulent leaves, in addition to its oil-rich seeds. Lettuce spread to the Greeks and Romans, the latter of whom gave it the name "''lactuca''", from which the English "lettuce" is ultimately derived. By 50 AD, multiple types were described, and lettuce appeared often in medieval writings, including several herbals. The 16th through 18th centuries saw the development of many varieties in Europe, and by the mid-18th century cultivars were described that can still be found in gardens. Europe and North America originally dominated the market for lettuce, but by the late 20th century the consumption of lettuce had spread throughout the world. Generally grown as a hardy annual, lettuce is easily cultivated, although it requires relatively low temperatures to prevent it from flowering quickly. It can be plagued with numerous nutrient deficiencies, as well as insect and mammal pests and fungal and bacterial diseases. ''L. sativa'' crosses easily within the species and with some other species within the ''Lactuca'' genus; although this trait can be a problem to home gardeners who attempt to save seeds, biologists have used it to broaden the gene pool of cultivated lettuce varieties. World production of lettuce and chicory for calendar year 2010 stood at 23 620 000/23,620,000 tonnes, half of which came from China. Lettuce is most often used for salads, although it is also seen in other kinds of food, such as soups, sandwiches and wraps; it can also be grilled. One variety, the Woju (莴苣) or asparagus lettuce, is grown for its stems, which are eaten either raw or cooked. Lettuce is a rich source of vitamin K and vitamin A, and is a moderate source of folate and iron. Contaminated lettuce is often a source of bacterial, viral and parasitic outbreaks in humans, including ''E. coli'' and ''Salmonella''. In addition to its main use as a leafy green, it has also gathered religious and medicinal significance over centuries of human consumption. == Taxonomy and etymology == ''Lactuca sativa'' is a member of the ''Lactuca'' (lettuce) genus and the Asteraceae (sunflower or aster) family.〔(【引用サイトリンク】title=''Lactuca sativa'' L )〕 The species was first described in 1753 by Carl Linnaeus in the second volume of his ''Species Plantarum''.〔(【引用サイトリンク】title=The Linnaean Plant Name Typification Project )〕 Synonyms for ''L. sativa'' include ''Lactuca scariola'' var. ''sativa'',〔 ''L. scariola'' var. ''integrata'' and ''L. scariola'' var. ''integrifolia''.〔(【引用サイトリンク】title=''Lactuca sativa'' L )〕 ''L. scariola'' is itself a synonym for ''L. serriola'', the common wild or prickly lettuce.〔(【引用サイトリンク】title=''Lactuca serriola'' L )〕 ''L. sativa'' also has many identified taxonomic groups, subspecies and varieties, which delineate the various cultivar groups of domesticated lettuce. Lettuce is closely related to several ''Lactuca'' species from southwest Asia; the closest relationship is to ''L. serriola'', an aggressive weed common in temperate and subtropical zones in much of the world. The Romans referred to lettuce as ''lactuca'' (''lac'' meaning milk in Latin), an allusion to the white substance, now called latex, exuded by cut stems.〔 This word has become the genus name, while ''sativa'' (meaning "sown" or "cultivated") was added to create the species name.〔Katz and Weaver, p. 376.〕 The current word ''lettuce'', originally from Middle English, came from the Old French ''letues'' or ''laitues'', which derived from the Roman name. The name ''romaine'' came from that type's use in the Roman papal gardens, while ''cos'', another term for romaine lettuce, came from the earliest European seeds of the type from the Greek island of Cos, a center of lettuce farming in the Byzantine period.〔Weaver, p. 172.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「lettuce」の詳細全文を読む スポンサード リンク
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