Field with Virginian tobacco ( Nicotiana tabacum )
Tobacco ( Latin Nicotiana ) is a genus of plants in the nightshade family (Solanaceae). With around 75 species , it is one of the more species-rich genera within this family. Many species produce nicotine or other alkaloids in the roots , which they store in the leaves and which serve to ward off predators. The varieties of the species Nicotiana tabacum and Nicotiana rustica , which are used for the production of tobacco products , are of particular economic importance .
In the genus Nicotiana both species that exist as a small one-year or perennial herbaceous plants grow with a size of 0.1 to 0.3 m, but larger, weichholzige shrubs , the m up to 2 are high and often even small trees with a height of up to 10 m. Occasionally the plants give off a foul odor. The roots are often brood-bearing . Crystal sand can be found in the shoot axes and leaves . The phellogen is formed under the epidermis , the inner phloem is fibrous. The glandular trichomes almost exclusively form multicellular heads; however, there are also single-celled heads.
The alternate leaves are stalked or sessile. The basal, stem-like leaves often develop different shapes, whereby the stem-like leaves are usually smaller and can merge into the bracts of the inflorescences. The leaf margins are whole or wavy. The leaves are usually 8 to 15 (2 to 100) cm long, the petioles are shorter than the leaf blades and evenly curved.
Inflorescences and flowers
The hermaphrodite flowers are five-fold with a double flower envelope . The calyx is radial symmetry or, more rarely, zygomorphic , with five equally long or irregular linear, triangular or awl-shaped sepal lobes . The lobes are usually shorter than the urn-shaped, cylindrical or bell-shaped fused part of the calyx, only in exceptional cases are they the same length. The radially symmetrical or zygomorphic corolla is five-fold; 5 to 90 mm long, funnel-shaped, tubular or saucer-shaped and very diverse in color. The petal lobes have an indented edge. The five stamens can end inside or outside the flower, the stamens are straight or strongly bent to the knee; have the same length within a flower or come in two lengths (4 + 1) or three lengths (2 + 2 +1). The anthers are fixed dorsally, can be yellow, green or purple, are 1.2 to 2.3 mm long and are then almost circular or 3.5 to 5.5 mm long and then with an egg-shaped, obovate or oblong shape.
Fruits and seeds
The 4 to 20 (28) mm long capsule fruits are septum-cleft and usually contain 100 to 5000 seeds. The seeds are almost spherical or almost kidney-shaped, sometimes elongated, with a length of 0.4 to 1.3 mm; the thousand grain mass is 0.1 grams.
The most important phytochemicals of the Nicotiana species are alkaloids belonging to the nicotinoids . In 54 of 64 species examined, nicotine was one of the most strongly represented alkaloids, in 28 of them even the alkaloid with the highest concentration. Nornicotine was found in 32 of the 64 species examined; it was the main alkaloid in only eight species, mostly when nicotine or other alkaloids were missing as important alkaloids. Anabasine was also found to be the main alkaloid in three ways .
With the species Nicotiana tabacum and Nicotiana rustica it could be proven that with 97% the largest proportion of nicotine is formed in the roots. It is transported to all other parts of the plant via the xylem and, in addition to the roots, is also deposited in the young leaves, stems and flowers. The proportion of nicotine in the dried, untreated leaves of the species Nicotiana tabacum and Nicotiana rustica, which are mainly cultivated for tobacco cultivation, is usually between 0.5 and 8%, but in Nicotiana tabacum up to 10% and in Nicotiana rustica up to 18% Nicotine detected. In the other species, the total proportion of alkaloids in the dried parts of the plant varies between 0.003% and 2.96% in the leaves and 0.027% and 2.46% in the roots.
The odorless or fragrant flowers often bloom in the evening hours, close again in sunlight or remain open. There are also self-pollinating species. There is a wide variety of pollination mechanisms within the Nicotiana genus . So occurs ornithophily (pollination by birds, such as Nicotiana africana and Nicotiana langsdorfii ) Chiropterophilie (pollination by bats , for example Nicotiana otophora ) Sphingophilie (pollination by enthusiasts , for example in Nicotiana sylvestris and Nicotiana alata ) and Psychophilie (pollination by butterflies , for example in Nicotiana forgetiana ).
A particular pest of the tobacco plant is the tobacco hawk caterpillar ( Manduca sexta ), which is insensitive to the neurotoxin nicotine. The plant reacts to the saliva of the caterpillar with an output of the hormone jasmonic acid , after five to ten minutes in the entire infected leaf, after 30 minutes in the entire plant. Green leaf fragrances then emanate from the wound , which are carried through the air for kilometers. After one hour, defense mechanisms are activated in the tobacco plant, so that after about five hours the production of digestive proteins for the caterpillar of the tobacco hawk begins. After a total of ten hours, the plant emits a whole cocktail of fragrances, which attracts a certain species of wasp, which parasitically lays its eggs in the caterpillars of the tobacco hawk. In the wild forms of tobacco in particular, neighboring plants also perceive the emission of messenger substances and react by switching their genes at an early stage.
The tobacco plant also recognizes beetles based on their saliva, whereupon they produce up to ten milligrams of nicotine per leaf within an hour, which corresponds roughly to the amount of nicotine in a cigarette . The nicotine acts on the nervous system of the beetle that eats the plant, which is paralyzed and eventually dies.
The natural range of the genus Nicotiana consists of three disjoint areas. Most species occur in South America , the second largest number of species is found in Australia and neighboring areas in the South Pacific , and the third independent area is in North America . A single species is also known from the African continent, this is related to the species otherwise native to Australia. In many cases the natural range has been increased by human influences. This human-caused spread can only be justified in some species through cultivation and consumption, often the spread of the seeds in the fur of domesticated animals and humans themselves is a likely cause. Such an increase in the distribution area is suspected of some Australian species, but also of South American species with occurrences along the Peruvian Andes .
The northern border of the South American range of the genus Nicotiana begins in the west south of the Ecuadorian city of Guayaquil on 2 Southern latitude , thence southeast through the Peruvian Andes and the northern center of Bolivia to the province of Chaco in Argentina . In central Paraguay , the border runs a little further north, and then ends roughly at the level of Rio de Janeiro at the 23rd southern parallel. In the areas south of this line, the genus is only absent in a few regions: on the one hand in the sections of the Atacama Desert in the north of the Región de Tarapacá , in the cold Chilean rainforests south of the 37th parallel south from the Río Bío Bío to the Strait of Magellan and in the southernmost regions of the continent in Patagonia and Tierra del Fuego . The species Nicotiana cordifolia is also endemic to the Alexander Selkirk Island (formerly Isla Más Afuera), about 800 kilometers west of the Chilean coast.
Australia and South Pacific
The species of the genus Nicotiana native to Australia and the islands of the South Pacific belong to the section Suaveolentes, which is restricted to this area . In Australia, representatives can be found in all states. The exact areas are limited by the amount of annual precipitation. In areas with annual rainfall between 150 and 200 centimeters (sometimes between 75 and 100 centimeters if there is a pronounced rainy season in summer), no Nicotiana can be found. The almost precipitation-free areas of the continent are also avoided. The greatest number of species and also the most common occurrence of individuals can be found in New South Wales and South Australia .
Nicotiana debneyi can also be found outside of Australia; the species is known from Lord Howe Island and New Caledonia . As the only species of the Suaveolentes sectionthat does not occur on the Australian continent, Nicotiana fragrans colonizesvarious islands in the South Pacific, for example the Île des Pins , Lifou , Tongatapu , Hiva Oa and Fatu Hiva , where it was probably introduced on the last three islands.
The species Nicotiana glauca from the Paniculatae section, native to Argentina, is naturalized in Australia. Natural hybrids with the native species Nicotiana suaveolens , Nicotiana simulans and Nicotiana goodspeedii are known.
The natural range of the species, which occur exclusively in North America, includes the area of the Great Basin in the west of the continent, expanded to include areas near the coast, which extend from southern Canada to the southern border of Mexico . Including the species that occur in both South and North America, the North American range extends in the south to Guatemala . Through human domestication and accidental displacement, the actual distribution area extends to some of the more eastern states of the USA.
Within the genre there is a great variability in the demands on the location. However, all species prefer strong sunlight and a water-permeable soil. These conditions are found, for example, in semi-deserts at low and high altitudes, rocky protrusions, fine scree, sandy and gravelly river banks, and dry washouts. Only in exceptional cases do the species grow in dense bush or grassland ; they cannot be found in forests .
Most species are found in temperate climates . Only a few species reach as far as tropical regions; heavy rainfall and high humidity can only be tolerated in connection with well-drained soil. Species that occur at higher altitudes are usually annual in order to take advantage of the relatively high temperatures of the growing season as opposed to the low annual average temperatures.
The genus Nicotiana was established by Carl von Linné . The scientific generic name Nicotiana honors the French diplomat Jean Nicot (1539–1604), who in 1560 sent tobacco seeds to France as consul of France in Lisbon .
The systematics of the nightshade family according to William D'Arcy and Armando Hunziker classify the genus Nicotiana in the subfamily Cestroideae close to the genera Petunia and Fabiana . Phylogenetic , molecular biological studies show, however, that the genus is in the basal position of a clade , which also contains the Australian tribe Anthocercideae, consisting of the genera Anthocercis , Anthotroche , Crenidium , Cyphanthera , Duboisia , Grammosolen and Symonanthus . In Richard Olmstead's phylogenetic system , this group forms the subfamily Nicotianoideae, which is placed as a sister clade to the subfamily Solanoideae.
Cladogram simplified to
Within the genus Nicotiana , 75 naturally occurring species are distinguished, which are divided into 13 sections. Molecular biological studies have shown that the Polydicliae section is not monophyletic , but contains the species of the Trigonophyllae section .
Tobacco was important as a medicinal plant in ophthalmology until the 17th century. As a useful plant , only two species are currently (2013) of economic importance, which form numerous varieties and from which many varieties have been bred. The most common type is the Virginian tobacco ( Nicotiana tabacum ), to which almost all varieties grown today belong. The tobacco harvest (2007) is mainly used for cigarettes after appropriate processing. In Germany, the varieties “Friedrichstaler”, “Havanna”, “Geudertheimer” and “Burley” were widespread until the end of the 20th century. These are dark varieties that have been used for cigars and as an admixture to dark cigarettes. Virginia is a current variety that is used as an admixture in light-colored cigarette brands. In some cases, farmer's tobacco ( Nicotiana rustica ) is also grown. There are also numerous species and varieties that are used as ornamental plants.
As early as 1586, the medicinal properties of the plant were described in the Tabacologia work of the doctor Johannes Neander . In 1598 a tobacco plantation was set up in the Palatinate to meet the demand for tobacco for medicinal purposes. Were prepared extracts , tinctures , infusions, pills , powders , syrups and ointments . The tobacco smoke enema that Johann Gottlieb Schaeffer developed to treat colic , pinched fractures, flatulence , constipation and other diseases became particularly popular . In 1587, Gilles Everaerts wrote a work on tobacco as a medicine, De herba panacea , which then also dealt with "drinking" smoke.
The dried, cured and stripped tobacco leaves (smoke herb) can in tobacco pipes or rotated as cigarettes , cigarillos and cigars smoked be. The toxic, addictive nicotine is largely burned off; only a small proportion evaporates and is inhaled. Consumption in the form of smokeless tobacco , snus , chewing tobacco and snuff is less common . Even the consumption of small amounts can lead to death from respiratory paralysis due to the high nicotine content . Consumption through inhalation, sniffing or chewing is also associated with considerable health risks, which can range from cardiovascular problems to circulatory disorders and impotence to various forms of carcinoma. Several of these risks are also associated with second-hand and third-party smoking .
The consumption of tobacco products significantly increases the risk of nicotine addiction .
After its discovery in 1763, nicotine was also used as an insecticide for pest control by using "tobacco broth", a brew made from tobacco leaves, against insects. Since this measure also affects beneficial insects that are worth protecting and because of the highly harmful effects of nicotine as a nerve poison , this method is no longer used. Nevertheless, it is still discussed as a home remedy for aphids on indoor plants .
Types and varieties of tobacco are also grown as ornamental plants. Among these are wild species such as the forest tobacco ( Nicotiana sylvestris ), which is up to 1.7 m high and has a strong scent at night, with long white flower tubes, or the many varieties of the decorative tobacco Nicotiana x sanderae , a cross between the red-flowered Nicotiana forgetiana and the white-flowered Nicotiana alata . This crossing resulted in offspring in many shades and at different heights, sometimes always scented, sometimes night-scented or even without scent. The "Scarlet King" is a dark scarlet blooming variety, around 60 cm high.
Tobacco is one of those plants whose genome has been best researched. It is preferred in genetic engineering research because it is not consumed by humans or animals and therefore cannot accidentally enter the food chain. Changes in the genome resulted in nicotine-free tobacco, for example; the production of drugs in tobacco plants has become a serious and successful branch of research.
The tobacco variety Nicotiana tabacum BEL W3 is one of the plants that are most sensitive to ozone and develop visible harmful characteristics. For bioindication , the macroscopically recognizable leaf damage is used as an action parameter.
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