:''This article is about the plant genus ''Cannabis''. For use as a psychoactive drug, see
Cannabis (drug). For use as a therapeutic drug, see
Medical Cannabis. For non-drug cultivation and uses, see
Hemp.''
'''Cannabis''' is a genus of
flowering plants that includes three putative species, ''Cannabis sativa'' L., ''Cannabis indica'' Lam., and ''Cannabis ruderalis'' Janisch. These three taxa are indigenous to
central Asia and surrounding regions. Industrial
hemp products are made from ''Cannabis'' plants selected to produce an abundance of fiber and minimal levels of
THC (Δ
9- tetrahydrocannabinol), one
psychoactive molecule that produces the "high" associated with
marijuana. The drug consists of dried flowers and leaves of plants selected to produce high levels of THC. Various extracts including
hashish and hash oil are also produced.
[Erowid. 2006. ''Cannabis'' Basics. Retrieved on 25 Feb 2007] The cultivation and possession of ''Cannabis'' for recreational use is outlawed in most countries.
Etymology
Main articles: Cannabis (etymology)
The plant name 'cannabis' is from
Greek 'κάνναβις' (''kánnabis''), via Latin ''cannabis'', originally a a Scythian or Thracian word, also loaned into Persian as ''kanab''. English ''
hemp'' (Old English hænep) may be an early loan (predating
Grimm's Law) from the same source.
The further origin of the Scythian term is uncertain. It may be of Semitic origin, Hebrew 'קַנַּבּוֹס' (qannabbôs).
Description
''Cannabis'' is an
annual,
dioecious,
flowering herb. The
leaves are
palmately compound, with
serrate leaflets. The first pair of leaves usually have a single leaflet, the number gradually increasing up to a maximum of about thirteen leaflets per leaf (usually seven or nine), depending on variety and growing conditions. At the top of a flowering plant, this number again diminishes to a single leaflet per leaf. The lower leaf pairs usually occur in an opposite
leaf arrangement and the upper leaf pairs in an alternate arrangement on the main stem of a mature plant.
''Cannabis'' usually has
imperfect flowers with
staminate "male" and
pistillate "female" flowers occurring on separate plants,
[Lebel-Hardenack, S. and S. R. Grant. 1997. Genetics of sex determination in flowering plants. ''Trends in Plant Science'' '2'(4): 130–136.] although
hermaphroditic flowers sometimes occur.
[1] Male flowers are borne on loose
panicles, and female flowers are borne on
racemes.
[2] It is not unusual for individual plants to bear both male and female flowers in some strains, a condition called monoecy.
[3] On
monoecious plants, flowers of both sexes may occur on separate
inflorescences, or on the same inflorescence.
,
terpenoids, and other volatile compounds are secreted by glandular
trichomes that occur most abundantly on the floral
calyxes and
bracts of female plants.
[4]
All known strains of ''Cannabis'' are
wind-pollinated[5] and produce "
seeds" that are technically called
achenes.
[6] Most strains of ''Cannabis'' are
short day plants,
[ with the possible exception of ''C. sativa'' subsp. ''sativa'' var. ''spontanea'' (= ''C. ruderalis''), which is commonly described as "auto-flowering" and may be day-neutral.]
''Cannabis'' is naturally diploid, having a chromosome complement of 2n=20, although polyploid individuals have been artificially produced.[Small, E. 1972. Interfertility and chromosomal uniformity in ''Cannabis''. ''Canadian Journal of Botany'' '50'(9): 1947-1949.]
Cannabis is a genus of flowering plant which includes one or more species. The plant is believed to have originated in the mountainous regions just north west of the Himalayas. It is also known as hemp, although this term usually refers to varieties of Cannabis cultivated for non-drug use. Cannabis plants produce a group of chemicals called cannabinoids which produce mental and physical effects when consumed. As a drug it usually comes in the form of dried buds or flowers(marijuana), resin (hashish), or various extracts collectively known as hashish oil.[ In the early 20th century, it became illegal in most of the world to cultivate or possess Cannabis for drug purposes.]
Reproduction
Breeding systems
Some ''Cannabis sativa'' seeds
''Cannabis'' is predominantly dioecious,[[7] although many monoecious varieties have been described.[8] Subdioecy (the occurrence of monoecious individuals and dioecious individuals within the same population) is widespread.]
As a result of intensive selection in cultivation, ''Cannabis'' exhibits many sexual phenotypes that can be described in terms of the ratio of female to male flowers occurring in the individual, or typical in the cultivar.[13] Dioecious varieties are preferred for drug production, where the female plants are preferred. Dioecious varieties are also preferred for textile fiber production, whereas monoecious varieties are preferred for pulp and paper production. It has been suggested that the presence of monoecy can be used to differentiate between licit crops of monoecious hemp and illicit dioecious drug crops.
Mechanisms of sex determination
''Cannabis'' has been described as having one of the most complicated mechanisms of sex determination among the dioecious plants.
Based on studies of sex reversal in hemp, it was first reported by K. Hirata in 1924 that an XY sex-determination system is present.[Bridges, C. B. 1925. Sex in relation to chromosomes and genes. ''American Naturalist'' '59': 127-137.] Soon thereafter, Schaffner disputed Hirata's interpretation,[14] and published results from his own studies of sex reversal in hemp, concluding that an X:A system was in use and that furthermore sex was strongly influenced by environmental conditions.
Since then, many different types of sex determination systems have been discovered, particularly in plants.[ Negrutiu, I., B. Vyskot, N. Barbacar, S. Georgiev, and F. Moneger. 2001. Dioecious plants; a key to the early events of sex chromosome evolution. ''Plant Physiology'' '127'(4): 418-424.]
Since the 1920s, a number of sex determination models have been proposed for ''Cannabis''. Ainsworth
''Dense raceme of carpellate flowers typical of drug-type varieties of ''Cannabis''
The question of whether heteromorphic sex chromosomes are indeed present is most conveniently answered if such chromosomes were clearly visible in a karyotype. ''Cannabis'' was one of the first plant species to be karyotyped, however, this was in a period when karyotype preparation was primitive by modern standards (see History of Cytogenetics). Heteromorphic sex chromosomes were reported to occur in staminate individuals of dioecious 'Kentucky' hemp, but were not found in pistillate individuals of the same variety. Dioecious 'Kentucky' hemp was assumed to use an XY mechanism. Heterosomes were not observed in analyzed individuals of monoecious 'Kentucky' hemp, nor in an unidentified German cultivar. These varieties were assumed to have sex chromosome composition XX.[15] According to other researchers, no modern karyotype of ''Cannabis'' had been published as of 1996.[Shao Hong and Robert C. Clarke. 1996. Taxonomic studies of Cannabis in China. ''Journal of the International Hemp Association'' '3'(2): 55-60. Retrieved on 25 Feb 2007] Proponents of the XY system state that Y chromosome is slightly larger than the X, but difficult to differentiate cytologically.[16]
More recently, Sakamoto and various co-authors[ Sakamoto, K., K. Shimomura, Y. Komeda, H. Kamada, and S. Satoh. 1995. A male-associated DNA sequence in a dioecious plant, ''Cannabis sativa'' L. ''Plant & Cell Physiology'' '36'(8): 1549-1554. Retrieved on 25 Feb 2007][ Sakamoto, K., T. Abe, T. Matsuyama, S. Yoshida, N. Ohmido, K. Fukui, and S. Satoh. 2005. RAPD markers encoding retrotransposable elements are linked to the male sex in ''Cannabis sativa'' L. ''Genome'' '48'(5): 931-936. Retrieved on 25 Feb 2007] have used RAPD to isolate several genetic marker sequences that they name Male-Associated DNA in Cannabis (MADC), and which they interpret as indirect evidence of a male chromosome. Several other research groups have reported identification of male-associated markers using RAPD and AFLP.[Törjék, O., N. Bucherna, E. Kiss, H. Homoki, Z. Finta-Korpelová, I. Bócsa, I. Nagy, and L. E. Heszky. 2002. Novel male specific molecular markers (MADC5, MADC6) for sex identification in hemp. ''Euphytica'' '127': 209-218.][ Ainsworth commented on these findings, stating that "It is not surprising that male-associated markers are relatively abundant. In dioecious plants where sex chromosomes have not been identified, markers for maleness indicate either the presence of sex chromosomes which have not been distinguished by cytological methods or that the marker is tightly linked to a gene involved in sex determination."]
Environmental sex determination is known to occur in a variety of species.[Tanurdzic, M. and J. A. Banks. 2004. Sex-determining mechanisms in land plants. ''Plant Cell'' '16' (suppl.): S61-71.] Many researchers have suggested that sex in ''Cannabis'' is determined or strongly influenced by environmental factors.[ Ainsworth reviews that treatment with auxin and ethylene have feminizing effects, and that treatment with cytokinins and gibberellins have masculinizing effects.][ It has been reported that sex can be reversed in ''Cannabis'' using chemical treatment.][Mohan Ram, H. Y., and R. Sett. 1982. Induction of fertile male flowers in genetically female ''Cannabis sativa'' plants by silver nitrate and silver thiosulfate anionic complex. ''Theoretical and Applied Genetics'' '62': 369-375.]
A PCR-based method for the detection of female-associated DNA polymorphisms by genotyping has been developed.[Journal of Industrial Hemp 2003 Vol 8 issue 1 page 5-9, Female-Associated DNA Polymorphisms of Hemp (''Cannabis sativa'' L.), Hong Shao, Shu-Juan Song, Robert C. Clarke ]
Aspects of ''Cannabis'' production and use
''Cannabis'' field seized by authorities
★ Medical Cannabis discusses its use as a medication.
★ Cannabis (drug) discusses its use as a recreational drug.
★ Spiritual use of cannabis discusses sacramental and religious use.
★ Hemp discusses its uses as a source of housing, oil, food, fibers, and industrial materials.
★ Cannabis (drug) cultivation discusses aspects of cultivation for medicinal and recreational drug purposes
★ Legality of cannabis focuses on the law and enforcement aspects of growing, transporting, selling and using cannabis as a drug.
★
★ Cannabis rescheduling in the United States
★
★ Drug policy of the Netherlands
★ Health issues and the effects of cannabis discusses the pharmacology, physical, and mental effects of ''Cannabis'' when used as drug.
References
1. Cristiana Moliterni, V. M., L. Cattivelli, P. Ranalli. and G. Mandolino. 2005. The sexual differentiation of ''Cannabis sativa'' L.: A morphological and molecular study. ''Euphytica'' '140'(1-2): 95-106. Retrieved on 25 Feb 2007
2. Bouquet, R. J. 1950. ''Cannabis''. United Nations Office on Drugs and Crime. Retrieved on 23 Feb 2007
3. Mignoni, G. 1999. ''Cannabis'' as a licit crop: recent developments in Europe. United Nations Office on Drugs and Crime. Retrieved on 5 Oct 2006
4. Mahlberg, Paul G. and Eun Soo Kim. 2001. THC (tetrahyrdocannabinol) accumulation in glands of ''Cannabis'' (Cannabaceae). ''The Hemp Report'' '3'(17). Retrieved on 23 Feb 2007
5. Clarke, Robert C. 1991. ''Marijuana Botany'', 2nd ed. Ron Publishing, California. ISBN 0-914171-78-X
6. Small, E. 1975. Morphological variation of achenes of ''Cannabis''. ''Canadian Journal of Botany'' '53'(10): 978-987.
7. Ainsworth, C. 2000. Boys and girls come out to play: the molecular biology of dioecious plants. ''Annals of Botany'' '86'(2): 211-221. Retrieved on 24 Feb 2007
8. de Meijer, E. P. M. 1999. ''Cannabis'' germplasm resources. In: Ranalli P. (ed.). ''Advances in Hemp Research'', Haworth Press, Binghamton, NY, pp. 131-151. ISBN 1-56022-872-5
9. Schumann, E., A. Peil, and W. E. Weber. 1999. Preliminary results of a German field trial with different hemp (''Cannabis sativa'' L.) accessions. ''Genetic Resources and Crop Evolution'' '46'(4): 399-407. Retrieved on 24 Feb 2007
10. Ranalli, P. 2004. Current status and future scenarios of hemp breeding. ''Euphytica'' '140'(1): 121-131.
11. Hirata, K. 1924. Sex reversal in hemp. ''Journal of the Society of Agriculture and Forestry'' '16': 145-168.
12. Schaffner, J. H. 1931. The fluctuation curve of sex reversal in staminate hemp plants induced by photoperiodicity. ''American Journal of Botany'' '18'(6): 424-430.
13. Truta, E., E. Gille, E. Toth, and M. Maniu. 2002. Biochemical differences in ''Cannabis sativa'' L. depending on sexual phenotype. ''Journal of Applied Genetics'' '43'(4): 451-462. Retrieved on 24 Feb 2007
14. Schaffner, J. H. 1929. Heredity and sex. ''Ohio Journal of Science'' '29'(1): 289-300.
15. Menzel, Margaret Y. 1964. Meiotic chromosomes of monoecious Kentucky hemp (''Cannabis sativa''). ''Bulletin of the Torrey Botanical Club'' '91'(3): 193-205.
16. Peil, A., H. Flachowsky, E. Schumann, and W. E. Weber. 2003. Sex-linked AFLP markers indicate a pseudoautosomal region in hemp (''Cannabis sativa'' L.). ''Theoretical and Applied Genetics'' '107'(1): 102-109.
See also
★ Medical Cannabis
★ Cannabis (drug)
★ Legality of cannabis by country
Further reading
★ ''Cannabis: A History'' (2005) Martin Booth ISBN 0-312-32220-8
★ ''UNODC: World Drug Report 2006, Chapter 2: Cannabis: Why We Should Care'' (2006)
★ EMCDDA drugs profile: Cannabis (2007)
External links
★ International Plant Names Index (IPNI)
★ The Endocannabinoid System Network (ECSN) - Contains medical information to the Endocannabinoid System
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