Tobacco - biology. I INTRODUCTION Tobacco, plant grown commercially for its leaves and stems, which are rolled into cigars, shredded for use in cigarettes and pipes, processed for chewing, or ground into snuff, a fine powder that is inhaled through the nose. Tobacco is the source of nicotine, an addictive drug that is also the basis for many insecticides (see Smoking). Tobacco is a member of the nightshade family. There are more than 70 species of tobacco, of which 45 are native to the Americas. The two cultivated species, common tobacco and wild tobacco, are annuals--they live only one growing season. Common tobacco is 1 to 3 m (3 to 10 ft) tall and has a thick, woody stem with few side branches. One plant typically produces 10 to 20 broad leaves that branch alternately from the central stalk. The leaf size depends on the strain. The narrow, trumpetshaped flowers are dark pink to almost white. Wild tobacco is about 0.6 m (2 ft) tall and has a stem that is more slender and less woody than common tobacco. The leaves have a short stalk that attaches to the stem. The flowers are pale yellow with five separate lobes. II GROWING AND HARVESTING Tobacco grows in tropical and temperate regions, and it can be grown as far north as Canada and Norway. It thrives best in areas with a frost-free growing season of 120 to 170 days, depending on the type of tobacco. Good-quality tobacco requires fertile, well-drained, moist soil and warm temperatures. Most types of tobacco are grown in full sun. Environmental factors influence the plant's characteristics. Soil, for example, can affect leaf size, texture, and color. Sandy soils tend to produce a relatively large leaf that is light in color and body, fine in texture, and burns with a weak aroma. Heavier soils, which contain silt and clay, tend to produce a small, dark leaf with a heavy body and a strong aroma when burned. Several strains of common tobacco are grown for use primarily in different tobacco products. In the United States, Virginia tobacco is the main tobacco used in cigarettes; most of it is grown in North Carolina, Georgia, and Virginia. Burley tobacco, which is grown mostly in Kentucky and Tennessee, is used in cigarettes and pipes. Several countries, including the United States, Turkey, and Cuba, grow cigar tobacco. Tobacco plants are susceptible to attack from a wide range of insects and bacterial, fungal, and viral diseases. To counteract these problems, tobacco farmers grow strains of tobacco that resist diseases and insects. By rotating crops (planting tobacco one year and a different crop in the same field the next year), farmers keep the population of tobacco pests in check by depriving them of tobacco plants on alternate years. Before planting, farmers may work a fungicide into the soil to control fungal diseases, such as blue mold and damping-off. They may also fumigate the soil to control nematodes--microscopic worms that infest the roots. Growers also use herbicides to control weeds and insecticides to control insects. The annual tobacco cultivation cycle begins with the planting of seeds. In the United States, seed planting begins in March in southern states and June in northern states. Tobacco seeds are extremely small: one million seeds (the potential yield of a single mature plant) weigh about 80 g (about 3 oz). Tobacco seeds are so tiny that they need special care to keep them from drying out once they begin sprouting. To keep young plants watered and weeded, growers sow the seeds in specially prepared seedbeds of fertile, loose soil, rather than directly in the field. One to two months after planting, the growers transplant the seedlings into the field--a labor-intensive process called setting the tobacco. As flowers form on the plants, growers remove them in a process called topping, which encourages more leaf growth. Tobacco is harvested 70 to 130 days after setting. The harvesting method used depends on the type of tobacco. For some tobaccos, farmers cut whole plants off at the ground and spear them onto a stick about 1 m (3 ft) long, called a tobacco stick. Each stick holds about six plants. For other tobaccos, farmers remove the mature leaves and string them on wires, leaving the rest of the plant to continue growing. III CURING AND AGING After tobacco is harvested, it is cured (dried), and then aged to improve its flavor. There are four common methods of curing tobacco: air curing, fire curing, flue curing, and sun curing. The curing method used depends on the type of tobacco and its intended use. Air-cured tobacco is sheltered from wind and sun in a well-ventilated barn, where it air dries for six to eight weeks. Air-cured tobacco is low in sugar, which gives the tobacco smoke a light, sweet flavor, and high in nicotine. Cigar and burley tobaccos are air cured. In fire curing, smoke from a low-burning fire on the barn floor permeates the leaves. This gives the leaves a distinctive smoky aroma and flavor. Fire curing takes three to ten weeks and produces a tobacco low in sugar and high in nicotine. Pipe tobacco, chewing tobacco, and snuff are fire cured. Flue-cured tobacco is kept in an enclosed barn heated by flues (pipes) of hot air, but the tobacco is not directly exposed to smoke. This method produces cigarette tobacco that is high in sugar and has medium to high levels of nicotine. It is the fastest method of curing, requiring about a week. Virginia tobacco that has been flue cured is also called bright tobacco, because flue curing turns its leaves gold, orange, or yellow. Sun-cured tobacco dries uncovered in the sun. This method is used in Greece, Turkey, and other Mediterranean countries to produce oriental tobacco. Sun-cured tobacco is low in sugar and nicotine and is used in cigarettes. Once the tobacco is cured, workers tie it into small bundles of about 20 leaves, called hands, or use a machine to make large blocks, called bales. The hands or bales are carefully aged for one to three years to improve flavor and reduce bitterness. IV PREPARATION OF TOBACCO PRODUCTS Tobacco products include cigarettes, cigars, and pipe tobacco, which are smoked; snuff, which is inhaled into the nose; and chewing tobacco, which is chewed but not swallowed. Tobacco is also used for nicotine products, such as insecticides and medicines to help people quit smoking. The nitrogen-rich stalks left after harvesting are used as a fertilizer in tobacco-growing regions. In the first stages of processing, the stems and veins are removed and the leaves are cut into strips. Various tobacco strains are then blended in rotating drums. For example, blends of bright, burley, and oriental tobaccos are used in cigarettes. Moisture-holding substances, such as apple juice or glycerin, and flavorings, such as honey, licorice, or mint, are sometimes added to the blends. The blended tobaccos are then chopped into small shreds. The tobacco used in cigarettes and cigars needs to be rolled. Cigarette machines roll tobacco in a special paper that burns slowly and evenly. A filter is often added to collect impurities and make the smoke less harsh to inhale. Cigars consist of three types of tobacco. The filler, or core, consists of small pieces of leaves, or small whole leaves. The binder holds the filler in place and is, in turn, covered by the wrapper, which is wound spirally, starting at the end that is to be lighted. Although some high- quality cigars are made entirely by hand, most cigars are manufactured by machine. Chewing tobaccos are generally made from thick grades of leaves to which binders and flavorings are added. Chewing tobacco is formed by pressing the tobacco into blocks known as plugs. Snuff is made by grinding tobacco into fine powder, which is then allowed to ferment for a long period of time. Frequently, snuff is scented with spices, such as jasmine or cloves. V TOBACCO INDUSTRY Over 6 million tons of commercial tobacco are grown each year. Leading tobacco-growing countries are China, Brazil, India, the United States, Zimbabwe, and Turkey. Tobacco is an economically important crop for many nations--more than 2 million tons of tobacco leaf, at a value of more than $6 billion, are exported each year worldwide. Brazil exports the most tobacco leaf. Some countries that grow and export tobacco also import foreign tobacco. For instance, the United States imports the same amount of tobacco as it exports. The United States exports the most cigarettes and manufactured tobacco products, accounting for nearly 20 percent of the world total. Japan is the largest importer of tobacco products. Cigarette consumption, which accounts for most tobacco use in the United States, reached a high of 4,345 cigarettes per person per year in 1963. This number has dropped steadily since 1964, when a special report by the U.S. surgeon general linked cigarette smoking with lung cancer, coronary artery disease, and other ailments. By 2002 yearly per capita consumption of cigarettes in the United States had dropped to about 1,980 cigarettes. As smoking became less popular in the United States and Europe, cigarette manufacturers have found new markets in eastern Europe, Asia, Africa, and the former Soviet Union. Due to the aggressive marketing efforts of the international tobacco industry, tobacco consumption in these areas is expected to rise by almost 3 percent annually. Since the Great Depression, the federal government has run price support programs for a variety of agricultural products, including rice, peanuts, and tobacco. The tobacco price support program stabilizes prices and ensures tobacco growers a fairly steady income. Farmers registered in the program belong to a cooperative association that sells their tobacco at auction. The cooperative buys, at a price set each year, any tobacco that the grower cannot sell. Although the federal government sponsors the cooperative association, it does not fund the purchase of unsold tobacco; that money comes from tobacco sales and association membership fees. The cooperative stores unsold tobacco and sells it the next year. VI HISTORY As early as 2,000 years ago, natives of the Americas used tobacco as a medicine, as a hallucinogen in religious ceremonies, and as offerings to the spirits they worshiped. When Italian Spanish explorer Christopher Columbus traveled to the Americas in 1492, he observed the Arawak people of the Caribbean smoking tobacco loosely rolled in a large tobacco leaf. They also smoked tobacco through a tube they called a tobago, from which the name tobacco originated. Columbus's crew introduced tobacco growing and use to Spain. During the next 50 years, sailors, explorers, and diplomats helped spread pipe and cigar smoking throughout Europe. At first, it was used medicinally as a purported treatment for diseases and disorders such as bubonic plague, migraines, labor pains, asthma, and cancer. Within 100 years, however, smoking for pleasure became common. In 1612 the British colony at Jamestown, Virginia, began growing wild tobacco and exporting it to England. They soon switched to common tobacco, the milder kind grown in the West Indies and in demand in Europe. It quickly became the main crop grown in the colonies and was so profitable that without it, historians agree, the English colonies in North America would have failed. As tobacco farming expanded through the colonies, growers brought British prisoners and debtors to work the fields. These indentured servants earned their freedom after 5 to 12 years of labor. Growers soon found it more profitable to bring in African slaves, since they never had to be given their freedom. Slavery enabled growers to farm larger areas, making giant plantations possible. After 1776 tobacco farming expanded from Virginia south to North Carolina and west as far as Missouri. In about 1864 an Ohio farmer happened upon a chlorophyll-deficient strain of tobacco called white burley, which became a main ingredient of American blended tobaccos. Cigarettes were invented in 1614 by beggars in Seville, Spain, a center for cigar production. The beggars collected scrap tobacco and rolled it in paper. However, snuff, cigars, and pipes remained the most popular means of using tobacco until the 19th century. Cigarette popularity rose when British soldiers fighting in the Crimean War (1853-1856) found the cigarettes of their Turkish allies to be more convenient than pipes or cigars. Cigarettes grew in popularity in the United States after the Civil War (1861-1865) but were relatively expensive because they were hand-rolled. Cigarette prices fell after American inventor James A. Bonsack patented a machine to roll cigarettes in 1880; the machines could produce more than 10,000 cigarettes in an hour. By 1919, cigarettes were more popular than cigars. Smoking continued to grow in popularity until the 1960s and 1970s, when awareness of its health risks grew. VII HEALTH EFFECTS Tobacco contains nicotine, an addictive drug. Tobacco smoke also contains more than 4,000 chemical compounds, including at least 43 cancer-causing compounds. Forms of tobacco that are smoked--cigarettes, pipes, and cigars--cause lung cancer, emphysema, and other respiratory diseases. Smoking also contributes to coronary heart disease and, in pregnant women who smoke, low birth weight of newborns. Chewing tobacco and inhaling snuff causes cancer of the mouth, nose, and throat and can lead to nicotine addiction. Cigarette smoking causes nearly 90 percent of all lung cancer cases. Inhaled tobacco smoke, from cigars and pipes as well as from cigarettes, also comes into direct contact with the tissues of the mouth, throat, and larynx, or voice box. Several studies have estimated that smokers are four to five times more likely to develop oral and laryngeal cancer than are nonsmokers. Studies have also linked smoking with the development of cancer in distant organs--that is, in organs not directly exposed to the smoke, such as the bladder, pancreas, kidney, stomach, liver, and uterus. Smoking also causes health problems in nonsmokers. Each year about 3,000 nonsmoking adults die of lung cancer as a result of breathing the secondhand smoke from others' cigarettes. Emphysema, the chronic narrowing and clogging of the airway passages in the lung, is the most common chronic lung disease. Its victims are almost exclusively smokers; it very seldom occurs in nonsmokers. However, not all smokers are susceptible to this disease; only 20 percent of heavy smokers will develop it. VIII ANTISMOKING ACTIONS IN THE UNITED STATES In light of the disease risks associated with tobacco products and their associated high health-care costs, many individuals and health organizations have lobbied for public policy changes that would change the way tobacco products are regulated, manufactured, marketed, and sold in the United States. In November 1998 the tobacco industry and the attorneys general of 46 states, along with representatives of the public health field and lawyers representing smokers, announced an agreement that bans outdoor cigarette advertising and the use of cartoon characters in advertising, a practice that may attract young people to smoking. The agreement also requires tobacco companies to pay $206 billion during the next 25 years to fund antismoking public education programs, smoking cessation programs, tobacco-related medical research, and reimbursement to states for some of the health-care costs associated with treating smokers. Although the tobacco settlement provides tobacco companies with some protection against further suits brought by states, it leaves open the possibility of lawsuits brought by individual smokers and their families for smoking-related health problems or deaths. Such suits have had mixed results in the United States. In several cases, juries relieved the tobacco companies of all responsibility, while in others, juries awarded individual smokers and their families millions of dollars in compensation for their losses. Representatives of the tobacco industry have long denied that smoking is addictive or a serious health risk. But in late 1999 Philip Morris (now known as Altria), the nation's largest cigarette maker, publicly acknowledged that smoking is addictive and causes life-threatening health problems. This action was considered a move to protect the company from future lawsuits by people who started smoking in recent years but claim they were unaware of the risks. Scientific classification: Tobacco plants belong to the nightshade family, Solanaceae. Common tobacco is classified as Nicotiana tabacum and wild tobacco as Nicotiana rustica. Contributed By: Erin Hynes Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.
