The leaves of Nicotiana tabacum, also called tobacco, contain large amounts of nicotine, a toxic, physically addictive alkaloid. Some 60,000 small farms grow N. tabacum in the United States, many of them in Kentucky and North Carolina. Although tobacco is a perennial species, it is cultivated as an annual. The roots manufacture the nicotine; the plant's vascular system carries it to large, hairy leaves where it is concentrated.
Some suggest that tobacco was named after habocq, a Caribbean name for a pipe in which it was smoked. Others say it came from Tobago, the Caribbean island where tobacco was originally grown. The genus name Nicotiana is said to come from Jean Nico, a French ambassador to Portugal, who introduced the plant to England in 1560.
Ethnobotanists estimate that tobacco was smoked 8,000 years ago in the Americas. Forest tribes that were secluded in South America for millennia smoked tobacco in pipes and in cigars, suggesting that smoking has long been an important ritual.
Christopher Columbus encountered tobacco on San Salvador on Oct. 13, 1492. On Nov. 2, he saw Cubans smoking cigars. By 1531, the Spaniards were growing tobacco in Haiti and Cuba; they shipped it to Spain by 1540. Andre Thevet imported seeds to France in 1556.
Sir Walter Raleigh took tobacco plants to England in 1586. In the Virginia colony, John Rolfe, later the husband of Pocahontas, began growing N. rustica in 1620, and N. tabacum in 1622. Queen Elizabeth I granted Rolfe a tobacco monopoly. In 1632, George Calvert, Lord Baltimore, began growing the Burley cultivar that Europeans came to prefer.
N. tabacum is one of eight species of the genus Nicotiana grown commercially, and it constitutes the bulk of tobacco used in cigarettes. N. rustica, also called Turkish tobacco, is the strongest species; its leaves contain up to 18 percent nicotine.
Tobacco seedlings grown in beds are transplanted to fields after eight weeks. The plant grows from 3 to 6 feet tall. The flowering stalks and branches are removed and the plants are given large amounts of nitrogen-rich fertilizer to promote the growth of the leaves.
The mature leaves are picked by machine or by hand before they are hung in a drying barn. Sometimes the entire plant is hung upside-down to dry. As the water content of the fermenting, drying leaves falls from 80 percent to 20 percent they change from green to yellow. Some of the sugars produced during the fermentation give tobacco its flavor.
The nicotine found in N. tabacum mimics acetylcholine, a neurotransmitter in the body. Nicotine does not turn into vapor when it is heated; it enters the bodily fluids through the mouth, throat and lungs and washes across the synapses or spaces between the nerves and muscles where it triggers electrical impulses. The body quickly uses acetylcholine, which is remade in the nerve cells. Nicotine must be broken down by the liver.
Nicotine causes cardiac irregularities including palpitation and vascular contraction and is a cause of the degeneration of arteries.
Tobacco Related Death
There are more than 170 unusual organic chemicals in tobacco including coumarin, a carcinogen. The American Heart Association estimates that 440,000 people die each year from diseases attributable to smoking. Smokers are killed by lung cancer and respiratory diseases and suffer numerous heart problems including vascular contractions, cardiac irregularities, palpitations and degeneration of the arteries. Pregnant women should not smoke.