Nicotiana

From Wikipedia, the free encyclopedia

Tobacco
Flowering Nicotiana tabacum
Scientific classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Subclass: Asteridae
(unranked) Euasterids I
Order: Solanales
Family: Solanaceae
Genus: Nicotiana
L.
Species

Numerous, see text

Nicotiana refers to a genus of herbs and shrubs of the nightshade family (Solanaceae) indigenous to North and South America, Australia, south west Africa and the South Pacific. Various Nicotiana species, commonly referred to as tobacco plants, are cultivated and grown to produce tobacco. Of all Nicotiana species, Cultivated Tobacco (N. tabacum) is the most widely planted and is grown worldwide for production of tobacco leaf for cigarettes. The genus is named in honor of Jean Nicot, who in 1561 was the first to present tobacco to the French royal court.

Many plants contain nicotine, a powerful neurotoxin that is particularly harmful to insects. However, tobaccos contain a higher concentration of nicotine than most other plants, and indeed nicotine was named after the tobacco plant. In addition, unlike many other Solanaceae they do not contain tropane alkaloids which are often poisonous to humans and other animals. Interesting to note that nicotine and tropane alkaloids, e.g. atropine found in datura stramonium, have exactly the opposite actions in the brain. While nicotine is an agonist of acetylcholine receptors, atropine acts as an antagonist at the same receptors. Tobacco leaves and sometimes stems are commonly used as entheogens and for pleasure. The leaves are processed into forms where they can be smoked, chewed, and sniffed.

In many industrialized countries, nicotine is among the most significant addictive substances and a cause for medical concern; see Health effects of tobacco smoking and Smokeless tobacco#Health issues for details. By contrast, in preindustrial societies, tobacco smoking was almost invariably considered a sacred or ritual activity and tightly regulated. Smoking a Native American "peace pipe" would invariably be preceded by paying due homage to the relevant deities and spirits and sacrificing some of the tobacco. Other cultures such as the Aztecs, while smoking tobacco more casually, were nonetheless aware of the fact that it is a potent and addictive drug. See also Religious views on smoking. Native peoples also used tobacco in other ways as an entheogen (e.g. as an additive to ayahuasca), and occasionally in ethnoveterinary medicine, e.g. to rid livestock of parasites.

Contents

[edit] Cultivation

Tobacco plantation
Tobacco plantation

Tobacco plants were long grown and/or harvested by local peoples. The Takelma for example utilized N. bigelovii, and tobacco was very important to the Aztecs who considered it one of the sacred herbs of Xochipilli, the "Flower Prince" (also known as Macuilxochitl, "Five Flowers"), a deity of agriculture and especially psychoactive plants. Indeed, the origins of Cultivated Tobacco (N. tabacum) are obscure; it is not known from the wild and appears to be a hybrid between Woodland Tobacco (N. sylvestris), N. tomentosiformis and another species (perhaps N. otophora), deliberately selected by humans a long time ago.[1]

In modern tobacco farming, Nicotiana seeds are scattered onto the surface of the soil, as their germination is activated by light. In colonial Virginia, seedbeds were fertilized with wood ash or animal manure (frequently powdered horse manure). Seedbeds were then covered with branches to protect the young plants from frost damage. These plants were left to grow until around April. Today, in the United States, unlike other countries, Nicotiana is often fertilized with the mineral apatite in order to partially starve the plant for nitrogen, which changes the taste of the tobacco.

After the plants have reached a certain height, they are transplanted into fields. This was originally done by making a relatively large hole in the tilled earth with a tobacco peg, then placing the small plant in the hole. Various mechanical tobacco planters were invented throughout the late 19th and early 20th century to automate this process, making a hole, fertilizing it, and guiding a plant into the hole with one motion.

Many species of Nicotiana are also grown as ornamental plants. They are popular vespertines, their sweet-smelling flowers opening in the evening to be visited by hawkmoths and other pollinators. Several tobacco plants have been used as model organisms in genetics. Tobacco BY-2 cells, derived from N. tabacum cultivar 'Bright Yellow-2', are among the most important research tools in plant cytology. Tobacco has played a pioneering role in callus culture research and the elucidation of the mechanism by which kinetin works, laying the groundwork for modern agricultural biotechnology.

[edit] Ecology, pests and diseases

Main article: List of tobacco diseases
Tobacco mosaic virus (electron micrograph)
Tobacco mosaic virus (electron micrograph)
Female Manduca sexta
Female Manduca sexta

Despite containing enough nicotine and/or other compounds such as germacrene and anabasine and other piperidine alkaloids (varying between species) to deter most herbivores,[2] a number of such animals have evolved the ability to feed on Nicotiana species without being harmed. Nonetheless, tobacco is unpalatable to many species and therefore some tobacco plants (chiefly Tree Tobacco, N. glauca) have become established as invasive weeds in some places.

In the nineteenth century, young tobacco plantings came under increasing attack from flea beetles (Epitrix cucumeris and/or Epitrix pubescens), causing destruction of half the United States tobacco crop in 1876. In the years afterward, many experiments were attempted and discussed to control the flea beetle. By 1880 it was discovered that replacing the branches with a frame covered by thin fabric would effectively protect plants from the beetle. This practice spread until it became ubiquitous in the 1890s.

Lepidoptera whose caterpillars feed on Nicotiana include:

These are mainly Noctuidae and some Sphingidae.

[edit] Selected species[3]

Nicotiana langsdorffii
Nicotiana langsdorffii
Nicotiana obtusifolia
Nicotiana obtusifolia
Nicotiana × sanderae ornamental cultivar
Nicotiana × sanderae ornamental cultivar

[edit] See also

[edit] Footnotes

  1. ^ Ren & Timko (2001)
  2. ^ Panter et al. (1990)
  3. ^ a b ITIS (1999)

[edit] References

Wikimedia Commons has media related to:
  • Integrated Taxonomic Information System (ITIS) (1999): Nicotiana. Retrieved 2007-NOV-20.
  • Panter, K.E.; Keeler, R.F.; Bunch, T.D. & Callan, R.J. (1990): Congenital skeletal malformations and cleft palate induced in goats by ingestion of Lupinus, Conium and Nicotiana species. Toxicon 28(12): 1377-1385. PMID 2089736 (HTML abstract)
  • Ren, Nan & Timko, Michael P. (2001): AFLP analysis of genetic polymorphism and evolutionary relationships among cultivated and wild Nicotiana species. Genome 44(4): 559-571. doi:10.1139/gen-44-4-559 PDF fulltext