Cannabis sativa
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Cannabis sativa L. is an annual flowering plant in the family Cannabaceae, first formally described by Carl Linnaeus in 1753.[1] It is the type species and, under the most widely accepted taxonomic treatment, the sole species of the genus Cannabis.[2] The species encompasses cultivated and wild forms used for fibre, seed and drug production, and has been cultivated across most of the inhabited world since antiquity.[3]
Cannabis sativa is dioecious, wind-pollinated and photoperiod-sensitive. Wild and feral populations persist across temperate Asia, and the species has naturalised in disturbed habitats on every continent except Antarctica.[4]
Taxonomic history
Linnaeus described Cannabis sativa from European hemp cultivars in 1753, placing it as the sole species of the genus Cannabis in the Urticaceae (now Cannabaceae).[1] In 1785, Lamarck described Cannabis indica as a separate species based on drug-type specimens from India, distinguishing it from European hemp by its shorter stature, firmer stem, thinner bark and more pronounced intoxicating properties.[5]
The question of whether Cannabis contains one species or several has persisted since Lamarck's description. Janischewsky described Cannabis ruderalis in 1924 from wild Russian populations characterised by small stature and spontaneous seed shattering.[3] Schultes and colleagues proposed a three-species model in 1974, distinguishing C. sativa (fibre hemp), C. indica (broad-leaflet drug type) and C. ruderalis (wild/feral).[6]
Small and Cronquist (1976) consolidated these into a single polymorphic species with two subspecies and four varieties, a treatment that remains the most widely applied formal taxonomy:[2]
- C. sativa subsp. sativa var. sativa — cultivated hemp
- C. sativa subsp. sativa var. spontanea Small & Cronquist — wild/feral hemp
- C. sativa subsp. indica (Lam.) E. Small & Cronquist — cultivated drug type
- C. sativa subsp. indica var. kafiristanica (Vavilov) Small & Cronquist — wild/feral drug type
Molecular studies have produced results consistent with either a single-species or multi-species interpretation. Hillig (2005) documented two major gene pools corresponding broadly to hemp and drug types but noted that the level of differentiation could support either taxonomic treatment.[7] Whole-genome resequencing by Ren et al. (2021) placed the basal divergence of Cannabis in the eastern Tibetan Plateau region, with an estimated divergence of basal hemp and drug lineages approximately 12,000 years ago, though this dating remains under discussion.[8]
For a full treatment of classification systems and the relationship between formal taxonomy and vernacular usage, see Cannabis Taxonomy, Sativa vs Indica and NLD/BLD classification.
Description
Habit
Cannabis sativa is an erect, branching annual herb. Plant height varies from less than 0.3 m in dwarf ruderal forms to over 5 m in fibre cultivars. Growth habit ranges from unbranched (typical of dense fibre plantings) to heavily branched (typical of drug-type plants grown at wide spacing). Stems are erect, ridged longitudinally and typically hollow in the internodes at maturity. The outer stem contains bast (phloem) fibres used in textile and cordage production.[4][3]
Leaves
Leaves are palmately compound and decussate (opposite) on the lower stem, becoming alternate in the upper stem and inflorescence region. Leaflets number one to thirteen per leaf, with five to nine being most common on mature vegetative growth. Leaflets are lanceolate with serrate margins, acute apices and cuneate bases. Leaflet width varies across populations: narrow-leaflet drug (NLD) types from South and Southeast Asian origins produce slender leaflets, while broad-leaflet drug (BLD) types from higher latitudes and altitudes produce wider leaflets with shorter internodes.[7][3]
The first true leaves (following the cotyledons) are simple or have only one to three leaflets. Leaflet number increases through the vegetative phase and decreases again as the plant transitions to flowering. Stipules are small, subulate and persistent at each node.[4]
Flowers
Cannabis sativa is predominantly dioecious. Staminate (male) flowers are borne in loose, pendulous panicles at branch tips and in leaf axils. Each staminate flower has five tepals (sepals) and five stamens with pendulous anthers that release wind-dispersed pollen. Staminate plants typically mature one to four weeks before pistillate plants and senesce shortly after pollen shed.[3]
Pistillate (female) flowers are sessile and borne in pairs at the nodes of short, densely packed racemes. Each pistillate flower consists of a single ovule enclosed by a thin perianth (perigonal bract), from which two elongated, plumose stigmas emerge. The perigonal bracts and subtending leaves of pistillate inflorescences are densely covered with glandular trichomes in drug-type forms, constituting the primary site of cannabinoid and terpenoid accumulation.[4]
Monoecious individuals bearing both staminate and pistillate flowers occur naturally at low frequency and can be induced by environmental stress, photoperiod manipulation or chemical treatment. Some fibre hemp cultivars have been bred for monoecy to ensure uniform maturation at harvest.[3]
Fruits and seeds
The fruit is an achene: a single-seeded, indehiscent, dry fruit enclosed in a persistent perianth. Achenes are ovoid to slightly compressed, 2–6 mm in length, smooth to slightly reticulate in surface texture and grey-green to brown in colour at maturity. A fleshy lipid-rich appendage (elaiosome) at the base may facilitate ant-mediated dispersal in wild populations.[4]
The seed within the achene consists of a thin testa surrounding a curved embryo with two cotyledons and a large endosperm. Seeds are rich in oil and protein and are used in food, animal feed and industrial oil production.[3]
In wild forms, achenes detach readily at maturity (seed shattering), a trait largely suppressed through domestication in both hemp and drug-type cultivars. Seed shattering is a key diagnostic character of C. sativa subsp. sativa var. spontanea and of Cannabis ruderalis in three-species treatments.[2]
Root system
The primary root is a taproot that can penetrate 1.5 m or more in loose soils. Lateral roots develop extensively in the upper soil horizon. Cannabis has not been shown to form mycorrhizal associations, a trait shared by relatively few angiosperm lineages.[4]
Distribution
The centre of origin of Cannabis is in temperate Asia, with the earliest divergence now placed in the eastern Tibetan Plateau and adjacent regions based on genomic evidence.[8] Wild and feral populations extend from the Caucasus through Central Asia to China, with the greatest morphological and genetic diversity concentrated in the Hindu Kush, western Himalaya and adjacent lowlands of South Asia.[3]
Human cultivation has carried C. sativa to every inhabited continent. Naturalised feral populations are established in temperate regions of North America, Europe, southern South America and temperate East Asia. In tropical regions, the species persists primarily as a cultivated plant, with landrace populations maintained by continuous farmer management rather than self-sustaining wild populations.[4]
Uses
Cannabis sativa has been exploited for three broadly distinct purposes, each associated with different plant forms and management regimes:
Fibre. Hemp cultivars selected for tall, unbranched growth and high bast fibre content have been cultivated for textile, cordage and paper production since prehistory. Fibre hemp is typically sown at high density to suppress branching and maximise stem length. These cultivars belong to C. sativa subsp. sativa in the Small and Cronquist system and generally contain low concentrations of THC.[4]
Seed and oil. Oilseed hemp cultivars are grown for achene production. Seeds are harvested for human food, animal feed and industrial oil extraction. These forms overlap with fibre cultivars and are sometimes dual-purpose.[3]
Drug production. Drug-type plants are grown for the resinous trichomes of the pistillate inflorescence, which accumulate THC, CBD and other cannabinoids and terpenoids. Drug-type landraces vary widely in growth form, chemical profile and management regime depending on geographic origin and end use (e.g. charas production in the Himalaya, ganja cultivation in South and Southeast Asia, kif in Morocco). These populations are classified as C. sativa subsp. indica by Small and Cronquist.[2][3]
The boundaries between these use categories are not rigid. Many traditional landrace populations serve multiple purposes, with fibre, seed and psychoactive resin harvested from the same or overlapping plantings depending on season and local need.[3]
Chemical variation
Cannabis sativa produces a complex mixture of secondary metabolites dominated by cannabinoids, terpenoids and flavonoids. The most abundant cannabinoids are THC (delta-9-tetrahydrocannabinol) and CBD (cannabidiol), whose relative proportions define the primary chemotypic classification:[4]
- Chemotype I — THC-dominant (drug type)
- Chemotype II — mixed THC/CBD
- Chemotype III — CBD-dominant (fibre/hemp type)
Additional rare chemotypes with elevated levels of cannabigerol (CBG), cannabichromene (CBC) or tetrahydrocannabivarin (THCV) have been documented in specific populations.[7] The genetic basis of the THC/CBD ratio is linked to allelic variation at the cannabinoid synthase loci, which have been mapped to a single genomic region.[9] Environmental factors including UV exposure, temperature and nutrient availability also influence final metabolite concentrations.[4]
Terpenoid profiles vary at the population level and have been investigated as a classification tool complementary to cannabinoid ratios.[10] For a botanical treatment of chemical variation in ecological context, see the Chemical ecology section of Cannabis Botany.
See also
References
- ↑ 1.0 1.1 Linnaeus, C. (1753). Species Plantarum, vol. 2, p. 1027. Stockholm: Laurentius Salvius.
- ↑ 2.0 2.1 2.2 2.3 Small, E. & Cronquist, A. (1976). A Practical and Natural Taxonomy for Cannabis. Taxon, 25(4), 405–435. doi:10.2307/1220524
- ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 Clarke, R.C. & Merlin, M.D. (2013). Cannabis: Evolution and Ethnobotany. University of California Press.
- ↑ 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 Small, E. (2015). Evolution and Classification of Cannabis sativa (Marijuana, Hemp) in Relation to Human Utilization. Botanical Review, 81(3), 189–294. doi:10.1007/s12229-015-9157-3
- ↑ Lamarck, J.-B. (1785). Encyclopédie Méthodique, Botanique, vol. 1, p. 695. Paris: Panckoucke.
- ↑ Schultes, R.E., Klein, W.M., Plowman, T. & Lockwood, T.E. (1974). Cannabis: an example of taxonomic neglect. Botanical Museum Leaflets, Harvard University, 23(9), 337–367.
- ↑ 7.0 7.1 7.2 Hillig, K.W. (2005). Genetic evidence for speciation in Cannabis (Cannabaceae). Genetic Resources and Crop Evolution, 52(2), 161–180. doi:10.1007/s10722-003-4452-y
- ↑ 8.0 8.1 Ren, G., Zhang, X., Li, Y., Ridout, K., Serber, M.L., et al. (2021). Large-scale whole-genome resequencing unravels the domestication history of Cannabis sativa. Science Advances, 7(29), eabg2286. doi:10.1126/sciadv.abg2286
- ↑ Laverty, K.U., Stout, J.M., Sullivan, M.J., Shah, H., Gill, N., Holbrook, L., et al. (2019). A physical and genetic map of Cannabis sativa identifies extensive rearrangements at the THC/CBD acid synthase loci. Genome Research, 29(1), 146–156. doi:10.1101/gr.242594.118
- ↑ Hazekamp, A. & Fischedick, J.T. (2012). Cannabis — from cultivar to chemovar. Drug Testing and Analysis, 4(7–8), 660–667. doi:10.1002/dta.407