Cannabis ( Cán-na-bis ) 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 South Asia. Cannabis has long been used for fibre (hemp), for medicinal purposes, and as a recreational drug. Industrial hemp products are made from Cannabis plants selected to produce an abundance of fiber and minimal levels of THC (Δ 9 - tetrahydrocannabinol), a psychoactive molecule that produces the "high" associated with marijuana. The psychoactive product 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 from the plant.
Etymology
Main article: Cannabis (etymology)The word cannabis is from Greek κάνναβις ( kánnabis ) (see Latin cannabis ), which was originally Scythian or Thracian. It is related to the Persian kanab , the English canvas and possibly even to the English hemp (Old English hænep ). In Hebrew, the word is קַנַּבּוֹס . Old Akkadian qunnabtu , Neo-Assyrian and Neo-Babylonian qunnabu were used to refer to the plant meaning "a way to produce smoke."
Description
Cannabis is an annual, dioecious, flowering herb. The leaves are palmately compound or digitate, 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 normally has imperfect flowers, with staminate "male" and pistillate "female" flowers occurring on separate plants. It is not unusual, however, for individual plants to bear both male and female flowers. Although monoecious plants are often referred to as "hermaphrodites," true hermaphrodites (which are less common) bear staminate and pistillate structures on individual flowers, whereas monoecious plants bear male and female flowers at different locations on the same plant. Male flowers are normally borne on loose panicles, and female flowers are borne on racemes.
All known strains of Cannabis are wind-pollinated and produce "seeds" that are technically called achenes. 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, like many organisms, is diploid, having a chromosome complement of 2n=20, although polyploid individuals have been artificially produced. The plant is believed to have originated in the mountainous regions northwest of the Himalayas. It is also known as hemp, although this term is often used to refer only 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. Cannabinoids, terpenoids, and other compounds are secreted by glandular trichomes that occur most abundantly on the floral calyxes and bracts of female plants. As a drug it usually comes in the form of dried flower buds (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.
Taxonomy
The genus Cannabis was formerly placed in the Nettle (Urticaceae) or Mulberry (Moraceae) family, but is now considered along with hops ( Humulus sp.) to belong to the Hemp family (Cannabaceae). Recent phylogenetic studies based on cpDNA restriction site analysis and gene sequencing strongly suggest that the Cannabaceae arose from within the Celtidaceae clade, and that the two families should be merged to form a single monophyletic group.
Various types of Cannabis have been described, and classified as species, subspecies, or varieties:
- plants cultivated for fiber and seed production, described as low-intoxicant, non-drug, or fiber types
- plants cultivated for drug production, described as high-intoxicant or drug types
- escaped or wild forms of either of the above types.
Cannabis plants produce a unique family of terpeno-phenolic compounds called cannabinoids, which produce the "high" one experiences from smoking marijuana. The two cannabinoids usually produced in greatest abundance are cannabidiol (CBD) and/or Δ 9 -tetrahydrocannabinol (THC), but only THC is psychoactive. Since the early 1970s, Cannabis plants have been categorized by their chemical phenotype or "chemotype," based on the overall amount of THC produced, and on the ratio of THC to CBD. Although overall cannabinoid production is influenced by environmental factors, the THC/CBD ratio is genetically determined and remains fixed throughout the life of a plant. Non-drug plants produce relatively low levels of THC and high levels of CBD, while drug plants produce high levels of THC and low levels of CBD. When plants of these two chemotypes cross-pollinate, the plants in the first filial (F 1 ) generation have an intermediate chemotype and produce similar amounts of CBD and THC. Female plants of this chemotype may produce enough THC to be utilized for drug production.
Whether the drug and non-drug, cultivated and wild types of Cannabis constitute a single, highly variable species, or the genus is polytypic with more than one species, has been a subject of debate for well over two centuries. This is a contentious issue because there is no universally accepted definition of a species. One widely applied criterion for species recognition is that species are "groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups." Populations that are physiologically capable of interbreeding, but morphologically or genetically divergent and isolated by geography or ecology, are sometimes considered to be separate species. Physiological barriers to reproduction are not known to occur within Cannabis , and plants from widely divergent sources are interfertile. However, physical barriers to gene exchange (such as the Himalayan mountain range) might have enabled Cannabis gene pools to diverge before the onset of human intervention, resulting in speciation. It remains controversial whether sufficient morphological and genetic divergence occurs within the genus as a result of geographical or ecological isolation to justify recognition of more than one species.
Early classifications
The Cannabis genus was first classified using the "modern" system of taxonomic nomenclature by Carolus Linnaeus in 1753, who devised the system still in use for the naming of species. He considered the genus to be monotypic, having just a single species that he named Cannabis sativa L. (L. stands for Linnaeus, and indicates the authority who first named the species). Linnaeus was familiar with European hemp, which was widely cultivated at the time. In 1785, noted evolutionary biologist Jean-Baptiste de Lamarck published a description of a second species of Cannabis , which he named Cannabis indica Lam. Lamarck based his description of the newly named species on plant specimens collected in India. He described C. indica as having poorer fiber quality than C. sativa , but greater utility as an inebriant. Additional Cannabis species were proposed in the 19th century, including strains from China and Vietnam (Indo-China) assigned the names Cannabis chinensis Delile, and Cannabis gigantea Delile ex Vilmorin. However, many taxonomists found these putative species difficult to distinguish. In the early 20th century, the single-species concept was still widely accepted, except in the Soviet Union where Cannabis continued to be the subject of active taxonomic study. The name Cannabis indica was listed in various Pharmacopoeias, and was widely used to designate Cannabis suitable for the manufacture of medicinal preparations.
20th Century
In 1924, Russian botanist D.E. Janichevsky concluded that ruderal Cannabis in central Russia is either a variety of C. sativa or a separate species, and proposed C. sativa L. var. ruderalis Janisch. and Cannabis ruderalis Janisch. as alternative names. In 1929, renowned plant explorer Nikolai Vavilov
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