Phenotypic plasticity
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Phenotypic plasticity is the capacity of a single cannabis genotype to produce different phenotypes in different environments. It is a large part of why Cannabis is so variable: much of the difference in height, form, flowering and chemistry between plants reflects the growing environment as well as inherited differences.[1][2] Because the same genotype can look and yield differently from one site or season to the next, a plant's field appearance is an unreliable guide to its genetic makeup, which matters for how landraces are described, compared and conserved.[3][4]
Plasticity is measured by growing the same genotypes across several environments and partitioning the variation into genetic, environmental and interaction components. The interaction term, genotype-by-environment interaction, captures the plastic response: how far genotypes rank or behave differently depending on where they are grown.[2][5]
Plastic traits in cannabis
Vegetative architecture is highly plastic. Across 200 or more accessions grown together, de Meijer and colleagues recorded plants from over four metres tall to dwarf forms under one metre, alongside wide variation in stem diameter and branching.[1] Height, branching and biomass respond strongly to sowing date, density, latitude and season, and cultivars often change rank for these traits between environments.[2]
Phenology is equally responsive. Cannabis is a short-day plant, and flowering begins when the daylength falls below a genotype's critical photoperiod, so the same genotype flowers earlier at a site where short days arrive sooner.[6][7] Flowering time and, in hemp and monoecious material, the balance of sex expression both shift with photoperiod and stress.[6]
The cannabinoids and terpenes are plastic in amount more than in kind. Naim-Feil and colleagues found that the ratios between cannabinoids, which define a plant's chemotype, stay fairly stable across growing facilities, while the absolute quantities vary with the environment.[4] Total cannabinoid content can be lowered by conditions such as high humidity, which also delays flowering.[8]
Environmental drivers
The environmental factors with the clearest effect on cannabis phenotype are photoperiod, light quantity and quality, temperature, water and nutrient supply, and planting density.[2][7] Photoperiod governs the switch to flowering, and the length of the pre-flowering long-day period trades floral biomass against cannabinoid potency.[7] Atmospheric humidity alters both chemistry and timing: elevated relative humidity reduces cannabinoid concentrations and delays flowering.[8] Site and season together can account for as much of the variation in cannabinoid content as genotype does.[5]
Plasticity and genotype
Separating the plastic component of a trait from its heritable component needs common-garden and multi-environment trials. In a two-year hemp study, genotype, year and their interaction each explained a similar share of the variation in cannabinoid accumulation, so the environmental and interaction components together exceeded genotype alone.[5] Petit and colleagues described some fibre-quality traits as governed by "plastic genetic systems", in which particular genes are expressed only in combination with particular conditions.[2]
Traits differ in how plastic they are. Qualitative characters such as cannabinoid ratio and sex are more strongly genetically determined and more repeatable across environments, while quantitative characters such as yield, height and total cannabinoid content are more plastic.[4][6] Genome-wide work on landraces has begun to map the loci behind this structure: a study of 145 Iranian landrace accessions resolved genomic regions associated with phenological, morphological and phytochemical traits, several of them pleiotropic.[9] Because so much visible variation is environmental, taxonomic and potency claims drawn from field-grown plants without a common-garden control are treated with caution.[4][10]
Significance for landraces and conservation
Plasticity is built into what a landrace is. An evolved landrace is a population shaped by natural and human selection within a defined environment, so part of its characteristic appearance is a plastic response to that setting rather than a fixed inherited trait.[3][11] Moved to a different climate, the same seed stock expresses differently, which is the environmental side of terroir.[11]
The point carries into conservation. A landrace grown far from its origin, or held only as a description of field-grown plants, cannot be assumed to show its source traits; telling heritable difference from plastic response needs the accessions grown side by side.[1][9] The same caution applies to ex situ collections, where growing conditions differ from the landrace's home ground.[3]
See also
References
- ↑ 1.0 1.1 1.2 de Meijer, E.P.M.; van der Kamp, H.J.; van Eeuwijk, F.A. (1992). "Characterisation of Cannabis accessions with regard to cannabinoid content in relation to other plant characters". Euphytica. 62 (3): 187–200. doi:10.1007/BF00041753.
- ↑ 2.0 2.1 2.2 2.3 2.4 Petit, J.; Salentijn, E.M.J.; Paulo, M.-J.; Thouminot, C.; van Dinter, B.J.; et al. (2020). "Genetic variability of morphological, flowering, and biomass quality traits in hemp (Cannabis sativa L.)". Frontiers in Plant Science. 11 102. doi:10.3389/fpls.2020.00102.
- ↑ 3.0 3.1 3.2 Casañas, F.; Simó, J.; Casals, J.; Prohens, J. (2017). "Toward an evolved concept of landrace". Frontiers in Plant Science. 8 145. doi:10.3389/fpls.2017.00145.
- ↑ 4.0 4.1 4.2 4.3 Naim-Feil, E.; Elkins, A.C.; Malmberg, M.M.; Ram, D.; Tran, J.; et al. (2023). "The cannabis plant as a complex system: interrelationships between cannabinoid compositions, morphological, physiological and phenological traits". Plants. 12 (3) 493. doi:10.3390/plants12030493.
- ↑ 5.0 5.1 5.2 Beleggia, R.; Menga, V.; Fulvio, F.; Fares, C.; Trono, D. (2023). "Effect of genotype, year, and their interaction on the accumulation of bioactive compounds and the antioxidant activity in industrial hemp (Cannabis sativa L.) inflorescences". International Journal of Molecular Sciences. 24 (10) 8969. doi:10.3390/ijms24108969.
- ↑ 6.0 6.1 6.2 Petit, J.; Salentijn, E.M.J.; Paulo, M.-J.; Denneboom, C.; Trindade, L.M. (2020). "Genetic architecture of flowering time and sex determination in hemp (Cannabis sativa L.): a genome-wide association study". Frontiers in Plant Science. 11 569958. doi:10.3389/fpls.2020.569958.
- ↑ 7.0 7.1 7.2 Dang, M.; Muthu Arachchige, N.; Campbell, L.G. (2022). "Optimizing photoperiod switch to maximize floral biomass and cannabinoid yield in Cannabis sativa L.: a meta-analytic quantile regression approach". Frontiers in Plant Science. 12 797425. doi:10.3389/fpls.2021.797425.
- ↑ 8.0 8.1 Corredor-Perilla, I.C.; Kwon, T.-H.; Park, S.-H. (2025). "Elevated relative humidity significantly decreases cannabinoid concentrations while delaying flowering development in Cannabis sativa L." Frontiers in Plant Science. 16 1678142. doi:10.3389/fpls.2025.1678142.
- ↑ 9.0 9.1 Babaei, M.; Torkamaneh, D. (2026). "Genetic architecture of phenological, morphological, and phytochemical traits in Cannabis landraces". The Plant Genome. 19 (2) e70243. doi:10.1002/tpg2.70243.
- ↑ Small, E. (2015). "Evolution and classification of Cannabis sativa (marijuana, hemp) in relation to human utilization". The Botanical Review. 81 (3): 189–294. doi:10.1007/s12229-015-9157-3.
- ↑ 11.0 11.1 Clarke, R.C.; Merlin, M.D. (2013). Cannabis: Evolution and Ethnobotany. Berkeley: University of California Press.