tobacco, any of numerous species of Nicotiana or the cured leaves of several of the species that are used after processing in various ways for smoking, snuffing, chewing, and extracting of nicotine. Common tobacco is Nicotiana tabacum, native to South America, Mexico, and the West Indies. Wild tobacco is Nicotiana rustica, the species cultivated by the Indians of eastern North America and presently cultivated in Turkey, the U.S.S.R., India, and several European countries. These two species were described by Linnaeus in 1753. Other species, such as N. attenuata, N. trigonophylla, and N. quadrivalvis, have been used for smoking by the Indians of western North America. Ornamental, flowering tobaccos are N. sylvestris and N. alata grandiflora. All species of Nicotiana are probably native to the Western Hemisphere except -several species native to Australia. Common tobacco may grow to a height of four to six feet (one to two metres) when not topped. The flowers, borne in a panicle, normally self-fertile, are usually pink but may be carmine or white. The leaves of some of the large varieties may reach a length of 2 to 3 feet, with a width of about half the length; but some of the Turkish, or Oriental, kinds, as grown commercially, may be less than 3 inches (7.6 centimetres) long. N. rustica varies from two to four feet in height and usually develops suckers, or axillary shoots. The leaves are thick and broadly oval; the flowers are pale yellow to greenish.

Both common tobacco and N. rustica have an epidermal covering of hairs, some of which are glandular and secrete a viscid liquid. Both species may have a high alkaloid content; that of N. rustica tends to be higher. Nicotine (q.v.), which characterizes tobacco, occurs along with related alkaloids and organic acids such as malic and citric. Nicotine content is determined by the species, variety, and strain of tobacco; the growing conditions, particularly soil and climate; the methods culture and cure; and the position on the plant from which the leaves are taken (lower leaves usually have less nicotine). There considerable variation in commercial tobacco, but on average the dark, air-cured and fire- cured types contain 4 to 4.5 percent nicotine; cigar filler and Burley contain 3.5 to 4 percent; flue-cured, 2.5 to 3 percent; Maryland, 2 percent; and Turkish, less than 2 percent. N. rustica has been grown with up to 10 percent nicotine in the leaf. During the fermentation or aging process, there is a loss in nicotine. cigar tobaccos, which are subjected to a heavy fermentation, one-half or more of the mcciine may disappear. Tobacco is high in ash content, which ranges from 15 to 25 percent of the leaf on a water- free basis. Flue-cured tobacco is rich in sugar, the cigarette grades having 15 to 20 percent more. Cigar tobaccos are high in nitrogenous compounds but are almost free of starch and sugars.

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Author Resource BoxI live in Middlesex, UK. I am a researcher for a company which manufactures agricultural supplies to the farms in the countyside. Married with 2 children.Read Ben Heus Profile