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Cannabis Cultivation  Research

 

 

First placed online April 2021

 

Due to the legality of high THC cannabis and low THC hemp there is a mounting body of research now starting to emerge surrounding cannabis production. Based on this, I thought it may be handy to be able to track and access this research via manicbotanix.com.  

 

Bookmark this page if you’d like to keep up with the latest scientific research surrounding commercial cannabis production. I’ll be updating this page regularly as new research is published.

 

As a tip, if the links posted on this page to the full academic paper don’t work, Google the title of the paper and that should lead you to the full text article. In some cases, the full paper may not be available freely online. In cases such as this, it is recommended to use Sci-hub – https://sci-hub.se/ – and search for a full open access copy of the paper there.

 

Cannabis Cultivation Research: Abstracts and Links to Papers – Use the Links to Scroll 

 

*Latest paper, Root Disease: July 2021 —–  Several Pythium species cause crown and root rot on cannabis (Cannabis sativa L., marijuana) plants grown under commercial greenhouse conditions

*New paper, Substrates: July 2021 Growing Mediums for Medical Cannabis Production in North America

*New paper, Nutrients: April 2021 —- Nitrogen supply affects cannabinoid and terpenoid profile in medical cannabis (Cannabis sativa L.)

*New paper, Light: April 2021 —— Cannabis Yield Increased Proportionally with Light Intensity, but Additional Ultraviolet Radiation Did Not Affect Yield or Cannabinoid Content

*New paper, Nutrients: March 2021 ——–  Response of medical cannabis (Cannabis sativa L.) genotypes to P supply under long photoperiod: Functional phenotyping and the ionome

*New paper, Extraction: April 2021 —- Extraction of Cannabinoids from Cannabis sativa L. (Hemp) — Review

March 2021, Light: High light intensities can be used to grow healthy and robust cannabis plants during the vegetative stage of indoor production

March 2021, Light:  Light matters: Effect of light spectra on cannabinoid profile and plant development of medical cannabis (Cannabis sativa L.)

March 2021, Nutrients: Impact of Phosphorus on Cannabis sativa Reproduction, Cannabinoids, and Terpenes

March 2021, Nutrients: Magnesium’s Impact on Cannabis sativa ‘BaOx’ and ‘Suver Haze’ Growth and Cannabinoid Production

March 2021, Nutrients: Iron Requirement in Cannabis Production

Nov 2020, Light:  The relationship between light intensity, cannabis yields, and profitability

Jan 2021, Light:  Cannabis yield, potency, and leaf photosynthesis respond differently to increasing light levels in an indoor environment

March 2021, THC testing discrepancies between labs: The frequency distribution of reported THC concentrations of legal cannabis flower products increases discontinuously around the 20% THC threshold in Nevada and Washington state

2018, Cloning Study: Vegetative propagation of cannabis by stem cuttings: effects of leaf number, cutting position, rooting hormone, and leaf tip removal

2019, Controlled Drought Stress: Increasing inflorescence dry weight and cannabinoid content in medical cannabis using controlled drought stress

2019, Coir Growing Study: Coir-based growing substrates for indoor cannabis production

2018, Propagation, Fertilisation, Substrates and Irrigation: Propagation and Root Zone Management for Controlled Environment Cannabis Production

2019, Nutrient Disorders and Sufficiency Ranges: Characterization of Nutrient Disorders of Cannabis sativa

2020, Sodium Chloride Tolerance of Cannabis: Aquaponic and Hydroponic Solutions Modulate NaCl-Induced Stress in Drug-Type Cannabis sativa L

2019, Cloning Study: Phenotypic plasticity influences the success of clonal propagation in industrial pharmaceutical Cannabis sativa

2020, Light Photoperiod: Night interruption lighting equally effective as daylength extension in retaining the vegetative state of Cannabis mother plants

2020, Cannabis Sufficiency Ranges: Augmenting Nutrient Acquisition Ranges of Greenhouse Grown CBD (Cannabidiol) Hemp (Cannabis sativa) Cultivars

2019, Cannabis Sufficiency Ranges: Expanding Leaf Tissue Nutrient Survey Ranges for Greenhouse Cannabidiol‐Hemp

2018, Lighting: The Effect of Light Spectrum on the Morphology and Cannabinoid Content of Cannabis sativa L.

2019, Nutrients: Response of Medical Cannabis (Cannabis sativa L.) Genotypes to K Supply Under Long Photoperiod.

2020, Nutrients: Response of Medical Cannabis (Cannabis sativa L.) to Nitrogen Supply Under Long Photoperiod

2018, Root Disease: Fusarium and Pythium species infecting roots of hydroponically grown marijuana (Cannabis sativa L.) plants

2020, Lighting Photoperiod: Photoperiodic Response of In Vitro Cannabis sativa Plants

2021, Light Spectrum and Yields: Cannabis lighting: Decreasing blue photon fraction increases yield but efficacy is more important for cost effective production of cannabinoids

2008, Light, Temperature and CO2: Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions

2011, Light, CO2: Photosynthetic response of Cannabis sativa L., an important medicinal plant, to elevated levels of CO2

2020, Tissue Culture: DKW basal salts improve micropropagation and callogenesis compared to MS basal salts in multiple commercial cultivars of Cannabis sativa

2021, Genetics: Widely assumed phenotypic associations in Cannabis sativa lack a shared genetic basis

 

 

 

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Several Pythium species cause crown and root rot on cannabis (Cannabis sativa L., marijuana) plants grown under commercial greenhouse conditions

 

July 2021

 

Abstract

Cannabis (Cannabis sativa L., marijuana) plants with symptoms of crown rot, root decay, wilting and plant death were sampled during 2018 and 2019 from seven production greenhouses. Affected tissues from 140 diseased plants were surface-sterilized and plated onto potato dextrose agar. Ninety-five isolates morphologically resembling Pythium species were subcultured and subjected to PCR of the ITS1-5.8-ITS2 region of ribosomal DNA. The following species were identified based on >99% sequence identity to reference isolates in GenBank: P. myriotylum (43 isolates), P. dissotocum (35 isolates), P. aphanidermatum (3 isolates) and Globisporangium ultimum (syn. P. ultimum) (2 isolates). A fifth species – P. catenulatum (12 isolates), was distinguished from P. rhizo-oryzae using the cytochrome oxidase c subunit I (COI) sequence. Cannabis licensed production facilities in British Columbia had all five species present, while P. dissotocum was found in two facilities in Ontario, and P. myriotylum was present in one facility in northern California. Isolates selected to represent each Pythium species were grown on potato dextrose agar at 25 oC and they all showed comparable colony growth after 6 days. The same isolates caused root browning, decay and stunting of cannabis plants grown in a coco: perlite potting medium. Plant mortality was similar after 21 days but rates of disease progression varied depending on the isolate tested. Wounding of roots and prolonged periods of saturation enhanced disease development. These results demonstrate for the first time that crown and root rot on greenhouse grown cannabis plants can be caused by up to five Pythium species.

 

Citation

Zamir K. Punja, Cameron Scott & Samantha Lung (2021) Several Pythium species cause crown and root rot on cannabis (Cannabis sativa L., marijuana) plants grown under commercial greenhouse conditions, Canadian Journal of Plant Pathology, DOI: 10.1080/07060661.2021.1954695

 

Abstract only link https://www.tandfonline.com/doi/abs/10.1080/07060661.2021.1954695

 

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Growing Mediums for Medical Cannabis Production in North America

 

July 2021

 

Abstract

 

The production and use of cannabis for medical purposes has been legalized in Canada and several states in the USA. Due to the historically illegal nature of cannabis, there is very little information available in academic publications about appropriate growing media for growing cannabis. The purpose of this review is to provide an overview of the most commonly used growing media for the production of medical cannabis and to discuss their advantages and disadvantages. Based on current knowledge, there is a general agreement on the properties of a suitable growing medium within the cannabis industry. However, there is little consensus among growers on the best growing medium to grow cannabis. Different categories of growing media are widely used in North America. In this review, we classified them into several main categories principally based on the type of material used in their composition and the growth stages of the plant. The main categories include: coir-based, peat-based, rockwool, phenolic foam, and living soil. It is not easy to suggest the best growing medium for cannabis production. Each category of growing medium has its strengths and weaknesses. Overall, it seems that coir-based products are the intermediate substrates showing more advantages and less weakness; however, choosing any of these categories depends a lot on the growing technique and production system. Future research should focus on determining the optimal level of growing media properties to produce high yielding medical cannabis with the desired quality.

 

Citation

 

Nemati R, Fortin J-P, Craig J, Donald S. Growing Mediums for Medical Cannabis Production in North America. Agronomy. 2021; 11(7):1366. https://doi.org/10.3390/agronomy11071366

 

Link to full text article https://www.mdpi.com/2073-4395/11/7/1366/htm

 

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Nitrogen supply affects cannabinoid and terpenoid profile in medical cannabis (Cannabis sativa L.)

 

 

April 2021

 

 

Highlights

 

  • N Supply affects cannabinoid and terpenoid concentrations in medical cannabis.

 

  • Tetrahydrocannabinolic acid and cannabidiolic acid decrease with the increase in N application.

 

  • Inflorescence yield is highest under 160–320 mg L−1 N.

 

  • Growth retardation and visual chlorosis are induced by N supply lower than 160 mg L−1 N, and N supply up to 320 mg L−1 did not induce a toxicity response.

 

  • The optimal N level for yield quantity, combined with relatively high secondary metabolite content, is 160 mg L−1 N.

 

 

Abstract

 

Secondary metabolism in plants is considerably affected by environmental factors including mineral nutrition. Nitrogen is a key plant nutrient, known to affect primary and secondary metabolism in plants, that its effect on the cannabis plants’ chemical profile is not known. To evaluate the hypothesis that N supply affects the cannabinoid and terpenoid profile, we studied the impact of N application on chemical and functional-physiology phenotyping in medical cannabis at the flowering stage. The plants were grown under five N treatments of 30, 80, 160, 240, and 320 mg L−1 (ppm) under environmentally controlled conditions. The results revealed that N supply affects cannabinoid and terpenoid metabolism, supporting the hypothesis. The concentrations of most cannabinoids and terpenoids tested were highest under the deficient concentration of 30 mg L−1 N and declined with the elevation of N supply. The concentrations of the two main cannabinoids, tetrahydrocannabinolic acid (THCA) and cannabidiolic acid (CBDA), decreased by 69% and 63%, respectively, with the increase in N supply from 30 to 320 mg L−1 N. Plant development and function were restricted under inputs lower than 160 mg L−1 N, demonstrating N deficiency. The morpho-physiological state of the plants was optimal at supply rates of 160–320 mg L−1 N. Inflorescence yield reflected the plant physiological state, increasing with the increase in N supply up to 160 mg L−1 N, and was unaffected by further increase in N. These results of the functional and chemical characterizations suggest that high N supply has adverse effects on the production of secondary compounds in cannabis, while it promotes growth and biomass production. Hence, N supply may serve for the regulation of the cannabinoid and terpenoid profiles, or for increasing plant yield, according to the desired production scheme. Taken together, the results reveal that the optimal N level for yield quantity, that allows also a relatively high secondary metabolites content, is 160 mg L−1 N. Finally, the present study provides a better understanding of the impact of N on ‘drug-type’ medical cannabis physiology, and takes us one step closer to the optimization of medical cannabis cultivation.

 

Citation

 

Avia Saloner, Nirit Bernstein. Nitrogen supply affects cannabinoid and terpenoid profile in medical cannabis (Cannabis sativa L.), Industrial Crops and Products, Volume 167, 2021,

 

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Response of medical cannabis (Cannabis sativa L.) genotypes to P supply under long photoperiod: Functional phenotyping and the ionome

 

 

March 2021

 

 

Highlights

 

Sensitivity analyses reveal a wide optimum range for P under short photoperiod.
Functional physiology and ionome profiling reveal genotypic variability in P sensitivity.
The threshold for optimal performance at the vegetative growth phase is about 30 mg L−1 P.
Excess P inhibits in-planta translocation of P and Mg.

 

 

Abstract

 

Phosphorus (P) is an essential macronutrient required for many central metabolic processes, and is therefore a major factor governing plant development, structure and function. Cannabis is a short-day plant that its’ development progression involves a vegetative growth phase under long photoperiod, followed by a reproductive phase under a short photoperiod. The reproductive inflorescence yield potential in cannabis is therefore largely dependent on the morphology and physiological condition of the plants at the vegetative phase. Due to legal restrictions, there is lack of science-based knowledge about cannabis plant science, including mineral nutrition. The present study therefore focused on P nutrition of plants at the vegetative growth phase under long photoperiod. The plants were cultivated in pots in a controlled environment and subjected to 5 levels of P (5, 15, 30, 60, 90 mg L−1). We investigated impact on the ionome, physiological and morphological traits, uptake of nutrients into the plant, translocation to the shoot, and distribution in the plant organs for 2 medicinal cannabis genotypes. Plant biomass production, photosynthesis rate, stomatal conductance, transpiration rate and intercellular CO2 at the vegetative growth phase exceled under 30 mg L−1 P supply. Uptake and translocation of nutrients from root to the shoot was highly influenced by the P treatment. Under excess P supply, most of the plant P accumulated in the roots, and translocation to the shoot was inhibited. Uptake of Mg into the plants, and its’ translocation to the shoot was inhibited by P deficiency in both cultivars, and was enhanced by increased P supply. Calcium uptake was increased by P application but translocation to the shoot was inhibited. Zinc retention in roots under P deficiency was found in both varieties. Our results suggest a wide optimum range for P in medicinal cannabis at the vegetative growth stage, with a minimum requirement of 15 mg L−1 P and a recommended application of 30 mg L−1. The functional physiology and ionome profiling revealed genotypic variability in P sensitivity.

 

Citation 

 

Sivan Shiponi, Nirit Bernstein. Response of medical cannabis (Cannabis sativa L.) genotypes to P supply under long photoperiod: Functional phenotyping and the ionome, Industrial Crops and Products, Volume 161, 2021

 

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Cannabis Yield Increased Proportionally with Light Intensity, but Additional Ultraviolet Radiation Did Not Affect Yield or Cannabinoid Content

 

 

Abstract

 

Cannabis (Cannabis Sativa L.) is now legally produced in many regions worldwide. Cannabis flourishes under high light intensities (LI); making it an expensive commodity to grow in controlled environments, despite its exceptionally high market value. It is commonly believed that cannabis secondary metabolite levels may be enhanced both by increasing LI and by exposing crops to ultraviolet radiation (UV). However, there is sparse scientific evidence to guide cultivators. Therefore, the impact of LI and UV on yield and quality must be elucidated to enable cultivators to optimize their lighting protocols. We explored the effects of LI, ranging from 350 to 1400 μmol m-2 s-1 and supplemental UV spectra on cannabis yield and potency. There were no spectrum effects on inflorescence yield, but harvest index under UVA+UVB was reduced slightly (1.6%) vs. the control. Inflorescence yield increased linearly from 19.4 to 57.4 g/plant and harvest index increased from 0.565 to 0.627, as LI increased from 350 to 1400 μmol m-2 s-1. Although there were no UV spectrum effects on total equivalent Δ9-tetrahydrocannabinol (T-THC) content in leaves, the neutral form, THC, was 30% higher in UVA+UVB vs. control. While there were no LI effects on inflorescence T-THC content, the content of the acid form (THCA) increased by 20% and total terpenes content decreased by 20% as LI increased from 350 to 1400 μmol m-2 s-1. High LI can substantially increase cannabis yield and quality, but we found no commercially-relevant benefits of adding supplemental UV radiation to indoor cannabis production.

 

Conclusion

 

Cannabis proliferates at very high canopy level LIs in indoor production. The linearly-increasing yield response to the broad range of LI levels (up to 1400 μmol m-2 s -1 ) in this trial clearly shows the benefits to maximizing canopy-level PPFD within the economical constraints imposed by other production logistics (including input costs). While increased yield did not have a major impact on cannabinoid composition, it did result in lower terpene content and further study is needed to assess the impact this has on product quality. Conversely, we saw no commercially-relevant benefits to exposing cannabis plants to UV radiation. Given the myriad potential UV exposure algorithms (i.e., combinations of spectrum, intensity, and temporal application strategies) more research is needed to determine whether UV treatments may be a commercially-relevant production tool and elucidate appropriate treatment protocols for commercial applications.

 

Citation

 

Llewellyn, D.; Golem, S.; Foley, E.; Dinka, S.; Jones, M.; Zheng, Y. Cannabis Yield Increased Proportionally With Light Intensity, but Additional Ultraviolet Radiation Did Not Affect Yield or Cannabinoid Content. Preprints 2021, 2021030327 (doi: 10.20944/preprints202103.0327.v1)

 

Full paper available https://www.preprints.org/manuscript/202103.0327/v1

 

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Extraction of Cannabinoids from Cannabis sativa L. (Hemp) — Review

 

April 2021

 

Abstract

 

Cannabis plant has long been execrated by law in different nations due to the psychoactive properties of only a few cannabinoids. Recent scientific advances coupled with growing public awareness of cannabinoids as a medical commodity drove legislation change and brought about a historic transition where the demand rose over ten-fold in less than five years. On the other hand, the technology required for cannabis processing and the extraction of the most valuable chemical compounds from the cannabis flower remains the bottleneck of processing technology. This paper sheds light on the downstream processing steps and principles involved in producing cannabinoids from Cannabis sativa L. (Hemp) biomass. By categorizing the extraction technology into seed and trichome, we examined and critiqued different pretreatment methods and technological options available for large-scale extraction in both categories. Solvent extraction methods being the main focus, the critical decision-making parameters in each stage, and the applicable current technologies in the field, were discussed. We further examined the factors affecting the cannabinoid transformation that changes the medical functionality of the final cannabinoid products. Based on the current trends, the extraction technologies are continuously being revised and enhanced, yet they still fail to keep up with market demands.

 

Conclusions

 

Fuelled by the recent opportunities provided by changing legislation, as well as the recent scientific advances, hemp’s product market capacity shows a historic jump off as high as 10 times in less than a decade. The tried extraction protocols are borrowed from those used traditionally for other biomasses, and the obtained results are, in some cases, contradictive for hemp, indicating that this step remains the bottleneck of hemp downstream processing technology. Among hemp products, CBD now has the greatest market potential and is highly attractive for its recreational and medical potentials. During CBD purification, the coextraction of its psychoactive cousin, THC, poses a significant challenge. Therefore, ideal extraction technology is expected to be not only cannabinoid-specific but also selective toward the extraction of CBD. Additionally, the chosen method needs to be safe, efficient (both in terms of economy and time), and capable of maximizing the yield (minimum CBD loss). Recent studies have demonstrated the successful application of supercritical fluids and organic solvents in the extraction of cannabinoids, terpenes, and fatty acids. Despite the effectiveness of organic solvents in extraction, the SC-CO2 seems to be superior in terms of operation economy, environmental concerns as well as large-scale purification technicalities.

 

Citation

Valizadehderakhshan M, Shahbazi A, Kazem-Rostami M, Todd MS, Bhowmik A, Wang L. Extraction of Cannabinoids from Cannabis sativa L. (Hemp)—Review. Agriculture. 2021; 11(5):384. https://doi.org/10.3390/agriculture11050384

 

Full text version available at https://www.mdpi.com/2077-0472/11/5/384

 

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High light intensities can be used to grow healthy and robust cannabis plants during the vegetative stage of indoor production

 

 

Abstract.

 

Although the vegetative stage of indoor cannabis production can be relatively short in duration, there is a high energy demand due to higher light intensities (LI) than the clonal propagation stage and longer photoperiods than the flowering stage (i.e., 16 – 24 hours vs. 12 hours). While electric lighting is a major component of both energy consumption and overall production costs, there is a lack of scientific information to guide cultivators in selecting a LI that corresponds to their vegetative stage production strategies. To determine the vegetative plant responses to LI, clonal plants of ‘Gelato’ were grown for 21 days with canopy-level photosynthetic photon flux densities (PPFD) ranging between 135 and 1430 µmol·m-2 ·s-1 on a 16-hour photoperiod (i.e., daily light integrals of ≈ 8 to 80 mol·m-2 ·d-1). Plant height and growth index responded quadratically; the number of nodes, stem thickness, and aboveground dry weight increased asymptotically; and internode length and water content of aboveground tissues decreased linearly with increasing LI. Foliar attributes had varying responses to LI. Chlorophyll content index increased asymptotically, leaf size decreased linearly and specific leaf weight increased linearly with increasing LI. Generally, PPFD levels of ≈ 900 µmol·m-2 ·s-1 37 produced compact, robust plants that are commercially relevant, while PPFD levels of ≈ 600 µmol·m-2 ·s-1 38 promoted plant morphology with more open architecture – to increase airflow and reduce the potential foliar pests in compact (i.e., indica-dominant) genotypes.

 

Conclusion

 

 Within the parameters of this investigation, we observed that PPFD levels between 600 and 900 µmol·m-2 ·s-1 appeared to achieve an appropriate balance in optimizing key morphological parameters in vegetative cannabis while minimizing energy use associated with excessively-high LIs and also considering different production strategies. Although the desired morphological and growth attributes of vegetative-stage clonal cannabis plants will be subjective to each genotype and production scenario, the presented LI responses can assist cultivators in optimizing the LI for their individual production goals; balancing the potential economic returns against elevated input costs associated with supplying more PAR to their crops.

 

 

Citation

 

Melissa Moher, David Llewellyn , Max Jones and Youbin Zheng (2021) High light intensities can be used to grow healthy and robust cannabis plants during the vegetative stage of indoor production.

School of Environmental Sciences and Department of Plant Agriculture, University of Guelph, 50 Stone Road East, Guelph, ON, N1G 2W1, Canada.

 

Full paper as PDF download  High Light Intensities Can Be Used to Grow Healthy and Robust Cannabis Plants During the Vegetative Stage of Indoor Production

 

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Light matters: Effect of light spectra on cannabinoid profile and plant development of medical cannabis (Cannabis sativa L.)

 

 

March 2021

 

 

Highlights

 

 

  • The cannabinoid profile is affected by light spectra.

 

  • The ratio of Blue: Red light affects cannabinoid metabolism.

 

  • CBGA accumulation is stimulated by Blue-rich light compared to Far-Red rich HPS light.

 

  • The response of CBDA, THCA and CBCA to light spectrum is cultivar specific.

 

  • A full spectrum does not improve inflorescence yield compared with Blue + Red light.

 

 

Abstract

 

 

Light is a key factor affecting plant growth, metabolism and function. Metabolic processes in plants are sensitive to the ratio of Blue:Red light, and there is an increasing awareness that the response to the ratio of these monochromatic lights may vary under exposure to a wider range of the spectrum, such as white light. Due to the potential for regulation of the therapeutic chemical profile and plant development, this issue is of growing interest for the cannabis (Cannabis sativa L.) industry that uses photosynthetic light extensively. Cannabis is a medicinal plant treasured for its secondary metabolites, especially cannabinoids, the unique biologically active compounds in the plant that are considered to be affected by light spectra. In this study we evaluated the hypothesis that the ratio of Blue:Red light affects cannabinoid metabolism, and that plant growth and secondary metabolism is intensified under a full spectrum with similar Blue:Red ratio. Our results point to several spectra specific reactions and some cultivar dependent responses to light spectrum. i. Yield quantity: The highest inflorescence yields were obtained when the spectrum was restricted to the red and blue range at the ratio of 1:1, and in two of the three varieties tested a ratio of 1:4 Blue:Red light had similar results. White light with Blue:Red ratio of 1:1 had the lowest yield. ii. The chemical profile was also affected by the light spectrum, and CBGA, the primary cannabinoid and a precursor for most other cannabinoids, demonstrated the highest response. CBGA accumulation was stimulated by blue-rich light as compared with far-red rich HPS light. The major cannabinoids CBDA, THCA and CBCA were also affected by light quality, and the response was cultivar specific and less pronounced than for CBGA. iii. Plant morphology: Blue light was most inductive for maintaining compact plants, more so than Red:Far-Red ratio. Our results repute the hypothesis that full spectrum improves inflorescence yield compared with Blue:Red light, but support the hypothesis that light spectrum influences plant development and the cannabinoid profile, which could be used to fine-tune cannabis and cannabinoid production.

 

 

Citation

 

 

Nadav Danziger, Nirit Bernstein. Light matters: Effect of light spectra on cannabinoid profile and plant development of medical cannabis (Cannabis sativa L.). Industrial Crops and Products, Volume 164, 2021, 113351, ISSN 0926-6690, https://doi.org/10.1016/j.indcrop.2021.113351.

 

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Impact of Phosphorus on Cannabis sativa Reproduction, Cannabinoids, and Terpenes

 

Abstract

 

Many abiotic factors, such as mineral nutrients—including phosphorus (P)—fertility, can impact the yield and growth of Cannabis sativa. Given the economic portion of C. sativa is the inflorescence, the restriction of P fertility could impact floral development and quality could be detrimental. This study sought to track the impacts of varying P concentrations (3.75, 7.50, 11.25, 15.0, 22.50, and 30.0 mg·L−1) utilizing a modified Hoagland’s solution. This experiment examined plant height, diameter, leaf tissue mineral nutrient concentrations, and final fresh flower bud weight as well as floral quality metrics, such as cannabinoids and terpenes. The results demonstrated that during different life stages (vegetative, pre-flowering, flowering), P concentrations impact C. sativa growth and development and yield. Regarding the cannabinoid pools, results varied for the individual cannabinoid types. For the acid pools, increasing fertility concentrations above 11.25 mg·L−1 P did not result in any increase in cannabinoid concentrations. These results indicate that, if a crop is being produced under greenhouse conditions, specifically for cannabinoid production, an excessive P supply did not result in higher cannabinoid production. However, plants grown with a higher rate of P fertility (30.0 mg·L−1) had greater plant width and may result in more buds per plant.

 

Conclusions

 

These results indicate that C. sativa has different fertility requirements based on the life stage and the end goal of production. For example, if a grower is producing mother stock plants for vegetatively propagated cuttings, plants will remain vegetative throughout their lifecycle. Thus, a concentration of 11.25 mg·L−1 P or greater may be adequate for this operation.

 

If C. sativa plants are to be grown for the florescence and/or cannabinoids or terpenes either for the fresh flower market or a distillate market, a P concentration above 11.25 mg·L−1 is preferred. While a P concentration of 22.5 mg·L−1 resulted in the greatest bud fresh weight when compared to the lowest two concentrations, it did not result in any greater increase in the active or acid cannabinoid pools. Additionally, higher P rates above 22.5 mg·L−1 did result in greater lateral production and consequently more nodes to produce the economic portion (floral material). Thus, a follow-up study should be completed to see if the increase in lateral nodes and floral material would result in a greater whole plant yield in floral material, despite the higher concentration of P resources not resulting in greater cannabinoid production in said flowers. Thus, for production in a cannabinoid or distillate market, a P fertility concentration of 11.25 mg·L−1 would be adequate, while for fresh market production, a P fertility concentration may be greater (22.5 mg·L−1) to account for more visually appealing floral material.

 

Additionally, these results indicate that the luxury consumption level for C. sativa regarding plant growth metrics and leaf tissue accumulation was not reached, given that no leveling off or plateauing of leaf tissue P was observed. This may indicate that C. sativa requires higher levels of P fertility to reach the uppermost limit of resource accumulation in the leaf tissue. Higher levels of P fertility concentrations should be explored to elucidate the uppermost levels of P resources the plant can acquire in the leaf tissue. Additional screening should be completed with other cultivars to quantify different P fertility needs more accurately for other types of C. sativa, given that a wide variety of plant architectures exists within C. sativa. Furthermore, the sampling of different plant parts (petioles, stems, roots etc.) for mineral nutrient concentration overtime would help illuminate the accumulation and reallocation of mineral resources within C. sativa over its life stages.

 

Paper found here https://www.mdpi.com/2076-3417/10/21/7875/htm

 

Reference for this paper. 

Cockson, P.; Schroeder-Moreno, M.; Veazie, P.; Barajas, G.; Logan, D.; Davis, M.; Whipker, B.E. Impact of Phosphorus on Cannabis sativa Reproduction, Cannabinoids, and Terpenes. Appl. Sci. 202010, 7875. https://doi.org/10.3390/app10217875

 

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Magnesium’s Impact on Cannabis sativa ‘BaOx’ and ‘Suver Haze’ Growth and Cannabinoid Production

 

Abstract

 

Limited research exists on the fertility needs for industrial hemp (Cannabis sativa) and the impact of fertility on plant growth and cannabinoids. Optimizing floral production for cannabinoid production and especially cannabidiol (CBD) production, is an economic goal for growers. Magnesium (Mg) is an essential nutrient for plant growth and plays many key roles in plant growth and when deficient leads to suboptimal plant growth. Six Mg fertility rates (0.0, 12.5, 25.0, 50.0, 75.0, and 100.0 mg·L-1) were evaluated to determine the optimal fertility for C. sativa on two High CBD-type cultivars ‘BaOx; and ‘Suver Haze’. Foliar Mg concentrations increased linearly for all life stages with the greatest foliar Mg concentrations being in the highest rate of 100.0 mg·L-1 Mg. Of the six rates, 50.0 and 75.0 mg·L-1 Mg optimized plant height, diameter, and plant total dry weight as well as having similar cannabinoid concentrations during the three life stages.

 

Conclusions

 

Growing ‘BaOx’ and ‘Suver Haze’ C. sativa with a fertility rate of 50.0 to 75.0 mg·L–1 provided maximum plant height, diameter, and total plant dry weight. These rates optimized plant growth without deficiency symptoms or stunting growth due to an over or under application. Although a plateau was not reached for the foliar accumulation of Mg, a plateau in which growth metrics were maximized occurred at a rate between 50.0 and 75.0 mg·L–1 Mg. Magnesium fertility had no impact on cannabinoid concentrations in which overall trends were not significant. Thus, growers can optimize yield and limit economic inputs between these rates or above if a more liberal fertility regime is desired.

 

Reference for this paper

 

Veazie, Patrick; Cockson, Paul; Logan, David; and Whipker, Brian (2021) “Magnesium’s Impact on Cannabis sativa ‘BaOx’ and ‘Suver Haze’ Growth and Cannabinoid Production,” Journal of Agricultural Hemp Research: Vol. 2 : Iss. 2 , Article 1. Available at: https://digitalcommons.murraystate.edu/jahr/vol2/iss2/1

 

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Iron Requirement in Cannabis Production

 

April 2021

 

Paul Cockson, Patrick Veazie, David Logan and Brian E. Whipker

 

New research explores optimal rates of iron in cannabis throughout its lifecycle.

 

Synopsis

 

Researchers look at optimal iron rates in cannabis production looking at six Fe fertility rates (0, 1, 2, 3, 3.5, and 4 parts per million (ppm). They explored the impacts of fertility rates on above-ground plant growth, leaf tissue nutrient accumulation and cannabinoids. The recommended rate for Fe fertility depends largely on your end product goals.

 

Findings

 

Biomass: Optimization of vegetative biomass production, such as what occurs in a fiber operation or mother stock management, was maximized early in the production cycle (first four weeks after transplant) at the highest (4 ppm Fe) fertility rate when compared to 0 ppm Fe treatment in the vegetative stage. After floral induction, biomass was generally similar during the reproductive stage regardless of Fe fertility. Thus, rates lower than 4 ppm can be used.

 

Leaf tissue: The upper ranges of Fe fertility (3.5 and 4 ppm) in the vegetative stage resulted in the greatest leaf tissue accumulation and appeared to level off given the values were statistically similar. For the pre-flowering and flowering stages, the highest fertility treatment (4 ppm Fe) resulted in the greatest leaf tissue levels, though a rate lower than this may be adequate given the high leaf tissue concentration present in the flowering stage was also within the recommended range.

 

Cannabinoids: When cannabinoids were analyzed, (CBDA, CBGA, THCA, Delta-9-THC), no clear trend was seen regarding an increase or decrease in concentrations when it came to Fe fertilization rate (Graph 1, p. 29). Given the variability seen in the cannabinoids data regarding Fe fertility, our recommendation for growers optimizing cannabinoids would be to utilize a fertility rate between 3 and 3.5 ppm given the adequate levels of Fe accumulation in the leaf tissue as reported.

 

Source for research found at Cannabis Business Times, full article @ https://www.cannabisbusinesstimes.com/article/iron-rate-fertility-cannabis-cultivation-plant-nutrition/

 

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The relationship between light intensity, cannabis yields, and profitability

 

J Eaves, November 2020

 

Abstract

 

The purpose of this study was to analyze the relationship between light intensity, cannabis (Cannabis sativa L.) yields, and profitability. We also look for evidence that spectrum differences across broad‐spectrum horticulture lights and general‐purpose LEDs affect the relationship between yield and light intensity. Finally, we discuss the financial return of increasing light intensity in order to increase yields. We found that yields increase linearly with light intensity up to at least 1500 µmol m–2 s–1, which is at least twice the intensity that is most commonly used by cannabis growers. That relationship did not appear to be influenced by spectrum quality differences among the lamps included in the study. Finally, for all the intensity ranges that we considered, the value of the gain in yields from increasing light intensity far exceeded the cost of using more electricity.

 

Findings

 

Our results show a positive, apparently linear relationship between intensity and yields which continues to at least 1498 µmol m–2 s–1, which is over twice the level provided by an HPS fixture in the grow configuration that is currently the industry standard. Moreover, holding light intensity constant, regarding yields, all the lamps spectrums appear to perform equally well. In other words, we find no evidence that the HPS lamp’s spectrum or the various tuned spectrums offered by specialty horticulture LED lights increase yields compared to a general-purpose, broad-spectrum LED lamp. It may be the case that spectrum tuning affects the chemical profile of the flower, but that question went beyond the scope of this study. Finally, the Master Grower judged that all the LED treatments for each run took about 5 d less than the HPS treatments to reach peak ripeness.

 

Paper found @ https://agnetix.com/app/uploads/2019/05/The-Profitablity-of-Growing-Cannabis-Under-High-Intensity-LightCR-Highlights.pdf

 

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Cannabis yield, potency, and leaf photosynthesis respond differently to increasing light levels in an indoor environment

 

Victoria Rodriguez Morrison, David Llewellyn, and Youbin Zheng

 

University of Guelph, Guelph, Ontario, Canada

 

8 January 2021

 

Abstract

 

Since the recent legalization of medical and recreational use of cannabis (Cannabis sativa L.) in many regions worldwide, there has been high demand for research to improve yield and quality. With the paucity of scientific literature on the topic, this study investigated the relationships between light intensity (LI) and photosynthesis, inflorescence yield, and inflorescence quality of cannabis grown in an indoor environment. After growing vegetatively for 2 weeks under a canopy-level photosynthetic photon flux density (PPFD) of ≈ 425 μmol·m-2·s-1 and an 18-h light/6-h dark photoperiod, plants were grown for 12 weeks in a 12-h light/12-h dark ‘flowering’ photoperiod under canopy-level PPFDs ranging from 120 to 1800 μmol·m-2·s-1 provided by light emitting diodes. Leaf light response curves varied both with localized (i.e., leaf-level) PPFD and temporally, throughout the flowering cycle.

 

Therefore, it was concluded that the leaf light response is not a reliable predictor of whole plant responses to LI, particularly crop yield. This may be especially evident given that dry inflorescence yield increased linearly with increasing canopy-level PPFD up to 1800 μmol·m-2·s-1, while leaf-level photosynthesis saturated well below 1800 μmol·m-2·s-1. The density of the apical inflorescence and harvest index also increased linearly with increasing LI, resulting in higher-quality marketable tissues and less superfluous tissue to dispose of. There were no treatment effects on cannabinoid potency, while there were minor LI treatment effects on terpene potency. Commercial cannabis growers can use these light response models to determine the optimum LI for their production environment to achieve the best economic return; balancing input costs with the commercial value of their cannabis products.

 

Full paper @ https://webcache.googleusercontent.com/search?q=cache:J8pdgj2YErcJ:https://www.preprints.org/manuscript/202101.0163/v1/download+&cd=2&hl=en&ct=clnk&gl=ca

 

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The frequency distribution of reported THC concentrations of legal cannabis flower products increases discontinuously around the 20% THC threshold in Nevada and Washington state

 

March 2021   

 

Background

 

Cannabis laboratory testing reliability is a scientific and policy challenge in US states with legal cannabis. Greater reported THC concentration yields higher prices, and media reports describe a well-known consumer and dispensary preference for flower products containing a minimum 20% THC content—an economically meaningful but biologically arbitrary threshold. This paper examines the frequency distribution of reported THC concentration in legal cannabis flower products in Nevada and Washington state for unusual shifts around the 20% threshold suggestive of potential manipulation of reported THC results.

 

Discussion

 

There is a statistically unusual spike in the frequency of products reporting just higher than 20% THC in both states consistent with economic incentives for products to contain at least 20% THC. This “bunching” of reported THC levels exists among some, but not all, cannabis testing labs, suggesting that laboratory differences (rather than precise manipulation by growers) drive this potential manipulation in reported THC content. These findings elaborate on prior research highlighting unexplained interlaboratory variation in cannabis testing results and highlight ongoing irregularities with legal cannabis testing.

 

Conclusion

 

These findings highlight the need for industry oversight and cautions researchers working with reported cannabis THC concentration data, which may be biased by economic incentives to report higher THC.

 

Research paper @ https://jcannabisresearch.biomedcentral.com/articles/10.1186/s42238-021-00064-2

Source: Zoorob, M.J. The frequency distribution of reported THC concentrations of legal cannabis flower products increases discontinuously around the 20% THC threshold in Nevada and Washington state. J Cannabis Res 3, 6 (2021). https://doi.org/10.1186/s42238-021-00064-2

 

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Vegetative propagation of cannabis by stem cuttings: effects of leaf number, cutting position, rooting hormone, and leaf tip removal

 

Abstract

 

This study evaluated the influence of several factors and their interactive effects on the propagation success of stem cuttings of cannabis (Cannabis sativa L.). Factors included (i) leaf number (two or three), (ii) leaf tip removal (one-third of leaf tips removed), (iii) basal/apical position of stem cutting on the stock plant, and (iv) rooting hormone [0.2% indole-3-butyric (IBA) acid gel or 0.2% willow (Salix alba L.) extract gel]. Cuttings were placed in a growth chamber for twelve days and then assessed on their rooting success rate and root quality using a relative root quality scale. The IBA gel delivered a 2.1× higher rooting success rate and 1.6× higher root quality than the willow extract. Removing leaf tips reduced rooting success rate from 71% to 53% without influencing root quality. Cuttings with three leaves had 15% higher root quality compared with those with two, but leaf number did not influence rooting success rate. Position of cutting had little effect on rooting success or quality. To achieve maximum rooting success and root quality, cuttings from either apical or basal positions should have at least three fully expanded uncut leaves and the tested IBA rooting hormone is preferred to the willow-based product.

 

Conclusions

 

Type of rooting hormone strongly influenced the success and quality of adventitious rooting in cannabis cuttings, with the 0.2% IBA gel delivering a higher rooting success rate than the 0.2% willow extract. Removing 30% of leaf tips from cuttings reduced rooting success rate and three leaves had higher root quality compared with two leaves without influencing rooting success rate. Position of cutting on the stock plant did not influence either rooting success rate or root quality. To achieve maximum rooting success and root quality, cuttings from either apical or basal positions should have at least three fully expanded uncut leaves and be dipped in an IBA rooting hormone. If a reduction in leaf area is desired, either because high humidity cannot be maintained or more airflow is desired in the propagation environment, then lowering the leaf number to two fully expanded leaves is preferential to cutting leaf tips.

 

Paper Reference:

 

Caplan, Deron et al. “Vegetative propagation of cannabis by stem cuttings: effects of leaf number, cutting position, rooting hormone, and leaf tip removal.” Canadian Journal of Plant Science 98 (2018): 1126 – 1132.

 

Link to paper https://cdnsciencepub.com/doi/full/10.1139/cjps-2018-0038

 

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Increasing inflorescence dry weight and cannabinoid content in medical cannabis using controlled drought stress

 

2019

 

Abstract:

 

Controlled application of drought can increase secondary metabolite concentrations in some essential oil-producing crops. To evaluate the effects of drought on cannabis (Cannabis sativa L.) inflorescence dry weight and cannabinoid content, drought stress was applied to container-grown cannabis plants through gradual growing substrate drying under controlled environment. Fertigation was withheld during week 7 in the flowering stage until midday plant water potential (WP) was approximately −1.5 MPa (drought stress threshold). This occurred after 11 days without fertigation. A well-irrigated control was used for comparison. Leaf net photosynthetic rate (Pn), plant WP, wilting (leaf angle), and volumetric moisture content (VMC) were monitored throughout the drying period until the day after the drought group was fertigated. At the drought stress threshold, Pn was 42% lower and plant WP was 50% lower in the drought group than the control. Upon harvest, drought-stressed plants had increased concentrations of major cannabinoids tetrahydrocannabinol acid (THCA) and cannabidiolic acid (CBDA) by 12% and 13%, respectively, compared with the control. Further, yield per unit growing area of THCA was 43% higher than the control, CBDA yield was 47% higher, ∆9-tetrahydrocannabinol (THC) yield was 50% higher, and cannabidiol (CBD) yield was 67% higher. Controlled drought stress may therefore be an effective horticultural management technique to maximize both inflorescence dry weight and cannabinoid yield in cannabis, although results may differ by cannabis cultivar or chemotype.

 

 

Citation

 

Caplan, D., Dixon, M., & Zheng, Y. (2019). Increasing Inflorescence Dry Weight and Cannabinoid Content in Medical Cannabis Using Controlled Drought Stress. Hortscience, 54, 964-969.

 

Link to paper https://journals.ashs.org/hortsci/view/journals/hortsci/54/5/article-p964.xml

 

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Coir-based growing substrates for indoor cannabis production

 

2019

 

Abstract:

Cannabis production for both medical and recreational purposes is an expanding industry in North America. Due to the historically illegal nature of this crop, scientific literature on cultivation is lacking, specifically with regards to growing substrate use and management. To evaluate coir-based growing substrates for the vegetative and flowering growth stages of cannabis production, two trials were conducted in walk-in growth chambers. In the first trial, plants were grown in three substrates: two coir-based organic substrates, i) ABcann UNIMIX 1 (U1); ii) ABcann UNIMIX 1 – HP (U1-HP) and a commercially available peat-based organic substrate; iii) PRO-MIX MP ORGANIK MYCORRHIZAE (PM-V). The coir-based substrates differed primarily in container capacity, U1 having higher container capacity (CC) than U1-HP. In the second trial, two other coir-based substrates were evaluated: i) ABcann UNIMIX 2 (U2); and ii) ABcann UNIMIX 2 – HP (U2-HP), with U2 having higher CC than U2-HP. Plants in both trials were container-grown and fertigated using liquid organic fertilizer at ≈30% substrate moisture content. In trial 1, after the 22-day vegetative growth period, all plants were transplanted into the same substrate and maintained under a 12-h photoperiod to initiate flowering and allow the measurement of dry floral weight (yield). Treatments in both trials were evaluated on their effects on plant health, growth rates and dry floral weight. It was concluded that either coir-based substrate (U1-HP or U1) is effective for cannabis production during the vegetative stage, and in the flowering stage, the drier coir-based substrates (U2-HP) may be preferred as it delivered 29% higher yield.

 

Citation

 

Caplan, D., Dixon, M. and Zheng, Y. (2019). Coir-based growing substrates for indoor cannabis production. Acta Hortic. 1266, 55-62
DOI: 10.17660/ActaHortic.2019.1266.9

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Propagation and Root Zone Management for Controlled Environment Cannabis Production

 

2018

 

Abstract:

Cannabis producers lack reliable information on the horticultural management of their crops. This thesis research was designed to improve horticultural practices for controlled environment cannabis production; topics included propagation, growing substrates, fertilization, and irrigation. To optimize the procedures for taking vegetative stem cuttings in cannabis, several factors were evaluated on how they affect rooting success and quality (Chapter Two). These included number of leaves, leaf tip removal, basal/apical position of cutting on the stock plant, and type of rooting hormone. Removing leaf tips reduced rooting success and cuttings with three fully-expanded leaves had higher rooting success and quality than those with two. Also, a 0.2% indole-3-butyric gel was more effective than a 0.2% willow extract gel to stimulate rooting and cutting position had no effect on rooting. Coir-based substrates with different physical properties were evaluated during the vegetative and flowering stage of cannabis production; optimal organic fertilizer rates were established for each substrate (Chapters Three and Four). During the vegetative stage, cannabis performed well in both tested substrates despite the ≈11% difference in container capacity (CC) between them. During the flowering stage, the substrate with lower CC increased floral dry weight (yield) and the concentration and/or yield of some cannabinoids, including THC, compared to the substrate with higher CC. The optimal organic fertilizer rate varied by substrate during the flowering stage but not during the vegetative stage; higher fertilizer rate during the flowering stage increased growth and yield but diluted some cannabinoids. Finally, the effects of controlled drought stress timing and frequency during the flowering stage were explored on floral dry weight and secondary metabolism (Chapters Five and Six). When drought was applied during week seven of the flowering stage, through gradual substrate drying over eleven days, floral concentration and content per unit growing area of major cannabinoids were increased. When drought was applied over a period of ≈8 days during week seven, cannabinoid content was similar to a well-watered control; though, dependent on drought timing, the content of some terpenoids varied. This research provided evidence-based information that can help growers improve the quality and yield of their cannabis crops.

 

Citation

 

Caplan, Deron. “Propagation and Root Zone Management for Controlled Environment Cannabis Production.” (2018).

 

Paper https://atrium.lib.uoguelph.ca/xmlui/bitstream/handle/10214/14249/Caplan_Deron_201808_PhD.pdf?sequence=5&isAllowed=y

 

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Characterization of Nutrient Disorders of Cannabis sativa

 

Abstract

 

Essential plant nutrients are needed at crop-specific concentrations to obtain optimum growth or yield. Plant tissue (foliar) analysis is the standard method for measuring those levels in crops. Symptoms of nutrient deficiency occur when those tissue concentrations fall to a level where growth or yield is negatively impacted and can serve as a visual diagnostic tool for growers and researchers. Both nutrient deficiency symptoms and their corresponding plant tissue concentrations have not been established for cannabis. To establish nutrient concentrations when deficiency or toxicity symptoms are expressed, Cannabis sativa ‘T1’ plants were grown in silica sand culture, and control plants received a complete modified Hoagland’s all-nitrate solution, whereas nutrient-deficient treatments were induced with a complete nutrient formula withholding a single nutrient. Toxicity treatments were induced by increasing the element tenfold higher than the complete nutrient formula. Plants were monitored daily and, once symptoms manifested, plant tissue analysis of all essential elements was performed by most recent mature leaf (MRML) tissue analysis, and descriptions and photographs of nutrient disorder symptomology were taken. Symptoms and progressions were tracked through initial, intermediate, and advanced stages.

 

Information in this study can be used to diagnose nutrient disorders in Cannabis sativa.

 

Citation

 

Cockson, P.; Landis, H.; Smith, T.; Hicks, K.; Whipker, B.E. Characterization of Nutrient Disorders of Cannabis sativaAppl. Sci. 20199, 4432. https://doi.org/10.3390/app9204432

 

Full text can be access @ https://www.mdpi.com/2076-3417/9/20/4432

 

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Aquaponic and Hydroponic Solutions Modulate NaCl-Induced Stress in Drug-Type Cannabis sativa L

 

2020

 

Abstract

The effects of salt-induced stress in drug-type Cannabis sativa L. (C. sativa), a crop with increasing global importance, are almost entirely unknown. In an indoor controlled factorial experiment involving a type-II chemovar (i.e., one which produces Δ9-tetrahydrocannabinolic acid ~THCA and cannabidiolic acid ~ CBDA), the effects of increasing NaCl concentrations (1-40 mM) was tested in hydroponic and aquaponic solutions during the flowering stage. Growth parameters (height, canopy volume), plant physiology (chlorophyll content, leaf-gas exchange, chlorophyll fluorescence, and water use efficiency), and solution physicochemical properties (pH, EC, and nutrients) was measured throughout the experiment. Upon maturation of inflorescences, plants were harvested and yield (dry inflorescence biomass) and inflorescence potency (mass-based concentration of cannabinoids) was determined. It was found that cannabinoids decreased linearly with increasing NaCl concentration: -0.026 and -0.037% THCA·mM NaCl-1 for aquaponic and hydroponic solutions, respectively. The growth and physiological responses to NaCl in hydroponic-but not the aquaponic solution-became negatively affected at 40 mM. The mechanisms of aquaponic solution which allow this potential enhanced NaCl tolerance is worthy of future investigation. Commercial cultivation involving the use of hydroponic solution should carefully monitor NaCl concentrations, so that they do not exceed the phytotoxic concentration of 40 mM found here; and are aware that NaCl in excess of 5 mM may decrease yield and potency. Additional research investigating cultivar- and rootzone-specific responses to salt-induced stress is needed.

 

Citation

 

Yep B, Gale NV, Zheng Y. Aquaponic and Hydroponic Solutions Modulate NaCl-Induced Stress in Drug-Type Cannabis sativa L. Front Plant Sci. 2020 Aug 5;11:1169. doi: 10.3389/fpls.2020.01169. PMID: 32849724; PMCID: PMC7424260.

 

Full Paper @ https://www.frontiersin.org/articles/10.3389/fpls.2020.01169/full

 

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Phenotypic plasticity influences the success of clonal propagation in industrial pharmaceutical Cannabis sativa

 

2019

 

Abstract

 

The burgeoning cannabis market requires evidence-based science such that farmers can quickly and efficiently generate new plants. In part, horticultural operations are limited by the success of cloning procedures. Here, we measured the role of environmental conditions and cultivar identity on the success of generating long branch material with many meristems in planting stock (mothers) and in rooting success of stem-derived clones. To evaluate the influence of lighting treatments on the optimal production of branching mothers, four lighting conditions (Fluorescent High Output T5s [T5], Metal halide lamps [MH], Plasma lamps [PL], or Metal halide lamps augmented with far red LED lights [MH+FR]) were applied to two cultivars of container grown plants (Cannabis sativa L. ‘Bubba Kush’, ‘Ghost Train Haze’) grown in peat-based organic substrates in mylar grow tents. To evaluate the influence of lighting, cutting tool (secateurs or scalpels), and stem wounding (present/absent) on optimal rooting of stems, three lighting conditions (Fluorescent T8s, T5, PL) were applied to three cultivars of peat pellet grown plants (Csativa L. ‘Bubba Kush’, ‘Ghost Train Haze’, ‘Headband’). Mothers grown under T5 and MH (vs MH+FR) produced ~30% more meristems. However, growing mothers under MH+FR were 19% taller than mothers under T5, with ~25% longer internodes on dominant stems than plants under any other lighting condition. Canopies were denser under T5 because petiole length was ~30% shorter under T5 and fan leaves were longer and narrower under MH+FR and MH+FR and PL, respectively, than under other lighting conditions. Cultivar Ghost Train Haze stems rooted most frequently and most quickly. Wounded stems were 162% more likely to root than unwounded stems and rooted 1.5 days earlier. Our results will guide producers attempting to maximize the rate of clone production in licensed facilities; although results may differ among cultivars, where cultivars differed in their average phenotype as mother plants, and their propensity to root from cuttings, and the speed with which they produced those roots.

 

Citation

 

Campbell LG, Naraine SGU, Dusfresne J. Phenotypic plasticity influences the success of clonal propagation in industrial pharmaceutical Cannabis sativa. PLoS One. 2019;14(3):e0213434. Published 2019 Mar 18. doi:10.1371/journal.pone.0213434

 

Full paper @ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6422331/

 

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Night interruption lighting equally effective as daylength extension in retaining the vegetative state of Cannabis mother plants

 

2020

 

Introduction

 

Cannabis is a short-day (SD) plant similar to poinsettia (Euphorbia pulcherrima) and chrysanthemum (Dendranthema × grandiflorum) (Nelson, 2012) and requires a scotoperiod of sufficient length to induce flowering. The critical night length (CNL) for Cannabis flowering is between 9 and 10 h (corresponding to 14–15 h of daylight) (Lisson, Mendham, & Carberry, 2000; Small, 2017), but the CNL varies by cultivar (Table 1). In order to induce flowering in Cannabis during greenhouse production, plants are provided with 12 hours of darkness (Lisson et al., 2000; Small, 2017). Mother stock plants used to generate cuttings for field production must be provided a daylength extension (DE) ≥16 hours to remain vegetative. In contrast, floriculture production utilizes night interruption (NI) lighting to retain the vegetative state of SD mother stock plants. No reports address the suitability of using NI for retaining the vegetative state of Cannabis. Therefore, this study compared 16-h DE lighting, to a truncated NI of 12 + 4 hours of lighting and with 12-h SD on the effects of photomorphogenesis of Cannabis.

 

Citation

 

Whipker BE, Cockson P, Smith JT. Night interruption lighting equally effective as daylength extension in retaining the vegetative state of Cannabis mother plants. Crop, Forage & Turfgrass Mgmt. 2020;6:e20001.

 

Full Paper can be found on Sci-hub

 

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Augmenting Nutrient Acquisition Ranges of Greenhouse Grown CBD (Cannabidiol) Hemp (Cannabis sativa) Cultivars

 

 

December 2020

 

Abstract

 

There is a growing interest in the production of hemp for the extraction of cannabidiol (CBD) due to reported therapeutic benefits. Recent policy reform has permitted state hemp pilot programs, including the land grant research institutions, the ability to investigate the potential of growing and harvesting Cannabis sativa plants (≤0.3% tetrahydrocannabinol) for these purposes in the U.S. There are vast gaps of knowledge regarding the fertility requirements of hemp cultivars grown in a horticultural production setting for floral attributes such as the cannabinoid constituents. Foliar tissue analysis provides an avenue to determine adequate ranges for nutrient uptake and estimating fertilizer requirements prior to visual symptoms of deficiency or toxicity. To facilitate a survey range of elemental nutrient acquisition in hemp cultivars propagated for CBD production, foliar analysis was executed using the most recently mature leaves (MRML) of mother stock plants. All plants were maintained in the vegetative stage for twelve weeks, prior to initiation of cutting for clone harvesting. A total of thirteen cultivars were utilized to broaden previously reported baseline survey ranges. Significant differences were found among all thirteen cultivars in accumulation of both micro and macro essential nutrients, widening the range of the fertility requirements of Cannabis plants grown in this production model for CBD harvesting.

 

Conclusions

 

The analysis of leaf tissue concentrations for both macro- and micronutrients in this survey found significant differences among CBD cultivars being used as vegetative mother stock prior to the harvesting of cuttings in a greenhouse setting. The acquired survey ranges exceed those previously reported, broadening the scope of fertility ranges for Cannabis sativa hemp cultivars. The survey ranges observed in this study suggest there are differences in acquisition and partitioning of nutrients based on the cultivar, and potentially subspecies, of the Cannabis sativa plant. Further research should be conducted to evaluate these dissimilarities in their entirety in addition to deficiency and toxicity thresholds to promote enhanced fertility management strategies of greenhouse cultivated hemp clonal varieties targeted for CBD production.

 

Citation

 

Kalinowski J, Edmisten K, Davis J, McGinnis M, Hicks K, Cockson P, Veazie P, Whipker BE. Augmenting Nutrient Acquisition Ranges of Greenhouse Grown CBD (Cannabidiol) Hemp (Cannabis sativa) Cultivars. Horticulturae. 2020; 6(4):98. https://doi.org/10.3390/horticulturae6040098

 

Full text https://www.mdpi.com/2311-7524/6/4/98/htm

 

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Expanding Leaf Tissue Nutrient Survey Ranges for Greenhouse Cannabidiol‐Hemp

 

 

2019

 

Abstract

 

Recent legislation allows US growers to produce industrial hemp (Cannabis sativa L.) under State Industrial Hemp Pilot Programs. Hemp can be produced for seed, fiber, or cannabidiol (CBD) (Johnson, 2018). Cannabidiol is a non-intoxicating cannabinoid, and products from CBD-hemp are considered to have one of the greatest market potentials due to its pharmaceutical value (Cherney and Small, 2016). There are no researched nutrient recommendations specific to greenhouse CBD-hemp, few resources for diagnosing plant nutrient problems, and little scientific research supporting greenhouse production. While there are Cannabis nutrient survey tissue values reported by Bryson and Mills (2014), it is unknown if these values are applicable for both field and greenhouse CBD-hemp crops or if differences exist among Cannabis cultivars. The purpose of this study was to determine if there were leaf tissue nutrient differences among industrial hemp cultivars being grown as stock plants for CBD-hemp production. In addition, the goal was to provide more precise nutrient survey tissue values that would aid in diagnosing nutrient disorders.

 

Conclusions

 

This study identified significant differences in leaf tissue nutrient concentrations among greenhouse grown CBDhemp Cannabis cultivars, which suggests nutrient uptake, partitioning, and/or utilization may differ among cultivars.

 

In addition, nutrient survey ranges reported in this study were outside of previously reported survey ranges for most nutrients, which broadens and further refines the target leaf tissue survey ranges for CBD-hemp stock plants being grown for transplants. Further research should be completed to determine nutrient sufficiency, deficiency, and toxicity ranges for greenhouse CBD-hemp cultivars at vegetative and flowering growth stages.

 

Citation

 

Landis, Hunter et al. “Expanding Leaf Tissue Nutrient Survey Ranges for Greenhouse Cannabidiol‐Hemp.” Crop, Forage and Turfgrass Management 5 (2019): 1-3.

 

Full paper available via Sci-hub

 

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The Effect of Light Spectrum on the Morphology and Cannabinoid Content of Cannabis sativa L.

 

2018

 

Abstract

 

Cannabis sativa L. flowers are the main source of Δ-9-tetrahydrocannabinol (THC) used in medicine. One of the most important growth factors in cannabis cultivation is light; light quality, light intensity, and photoperiod play a big role in a successful growth protocol. The aim of the present study was to examine the effect of 3 different light sources on morphology and cannabinoid production. Cannabis clones were grown under 3 different light spectra, namely high-pressure sodium (HPS), AP673L (LED), and NS1 (LED). Light intensity was set to ∼450 µmol/m2/s measured from the canopy top. The photoperiod was 18L: 6D/21 days during the vegetative phase and 12L: 12D/46 days during the generative phase, respectively. At the end of the experiment, plant dry weight partition, plant height, and cannabinoid content (THC, cannabidiol [CBD], tetrahydrocannabivarin [THCV], cannabigerol [CBG]) were measured under different light treatments. The experiment was repeated twice. The 3 light treatments (HPS, NS1, AP673L) resulted in differences in cannabis plant morphology and in cannabinoid content, but not in total yield of cannabinoids. Plants under HPS treatment were taller and had more flower dry weight than those under treatments AP673L and NS1. Treatment NS1 had the highest CBG content. Treatments NS1 and AP673L had higher CBD and THC concentrations than the HPS treatment. Results were similar between experiments 1 and 2. Our results show that the plant morphology can be manipulated with the light spectrum. Furthermore, it is possible to affect the accumulation of different cannabinoids to increase the potential of medicinal grade cannabis. In conclusion, an optimized light spectrum improves the value and quality of cannabis. Current LED technology showed significant differences in growth habit and cannabinoid profile compared to the traditional HPS light source. Finally, no difference of flowering time was observed under different R:FR (i.e., the ratio between red and far-red light).

 

Conclusion

 

These two experiments are part of a trial series aimed to study the effect of light conditions on cannabis growth. In conclusion, the experiments presented here demonstrate that the optimal spectrum for a specific photoperiod scheme may have diverse beneficial effects on cannabis growth, yield, and cannabinoid profile. Our study shows that the light environment plays an important role not only in plant size and stature but also in the accumulation of cannabinoids. During a long photoperiod, a low R:FR ratio is preferable to make more developed long cuttings, while during a short photoperiod a high proportion of blue irradiation is suitable to improve the medicinal value of cannabis in terms of cannabinoid content. Manipulation of the spectrum, an advantage of the LED technology, offers better space utilization to support the heating and cooling loads of growing buildings. LED lighting strategies may be applied to improve the energy utilization and carbon footprint of cannabis crop. The mechanisms underlying the effect of UV-A/blue light wavelength on cannabinoid pathways require further elucidation.

 

Citation

 

Magagnini, G., Grassi, G., & Kotiranta, S. (2018). The Effect of Light Spectrum on the Morphology and Cannabinoid Content of Cannabis sativa L. Medical Cannabis and Cannabinoids, 1, 19 – 27.

 

Full paper https://www.karger.com/Article/Fulltext/489030

 

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Response of Medical Cannabis (Cannabis sativa L.) Genotypes to K Supply Under Long Photoperiod.

 

2019

 

Abstract

 

Potassium is involved in regulation of multiple developmental, physiological, and metabolic processes in plants, including photosynthesis and water relations. We lack information about the response of medical cannabis to mineral nutrition in general, and K in particular, which is required for development of high-grade standardized production for the medical cannabis industry. The present study investigated the involvement of K nutrition in morphological development, the plant ionome, photosynthesis and gas-exchange, water relations, water use efficiency, and K use efficiency, comparatively for two genotypes of medical cannabis, under a long photoperiod. The plants were exposed to five levels of K (15, 60, 100, 175, and 240 ppm K). Growth response to K inputs varied between genotypes, revealing genetic differences within the Cannabis sativa species to mineral nutrition. Fifteen ppm of K was insufficient for optimal growth and function in both genotypes and elicited visual deficiency symptoms. Two hundred and forty ppm K proved excessive and damaging to development of the genotype Royal Medic, while in Desert Queen it stimulated rather than restricted shoot and root development. The differences between the genotypes in the response to K nutrition were accompanied by some variability in uptake, transport, and accumulation of nutrients. For example, higher levels of K transport from root to the shoot were apparent in Desert Queen. However, overall trends of accumulation were similar for the two genotypes demonstrating competition for uptake between K and Ca and Mg, and no effect on N and P uptake except in the K-deficiency range. The extent of accumulation was higher in the leaves > roots > stem for N, and roots > leaves > stem for P. Surprisingly, most micronutrients (Zn, Mn, Fe, Cu, Cl) tended to accumulate in the root, suggesting a compartmentation strategy for temporary storage, or for prevention of access concentrations at the shoot tissues. The sensitivity of net-photosynthetic rate, gas exchange, and water use efficiency to K supply differed as well between genotypes. The results suggest that growth reduction under the deficient supply of 15 ppm K was mostly due to impact of K availability on water relations of the tissue and transpiration in Royal Medic, and water relations and carbon fixation in Desert Queen.

 

Citation

 

Saloner A, Sacks MM, Bernstein N. Response of Medical Cannabis (Cannabis sativa L.) Genotypes to K Supply Under Long Photoperiod. Frontiers in Plant Science. 2019 ;10:1369. DOI: 10.3389/fpls.2019.01369.

Full text available https://europepmc.org/article/pmc/pmc6876614

 

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Response of Medical Cannabis (Cannabis sativa L.) to Nitrogen Supply Under Long Photoperiod

 

2020

 

The development progression of medical cannabis plants includes a vegetative growth phase under long photoperiod, followed by a reproductive phase under short photoperiod. Establishment of plant architecture at the vegetative phase affects its reproduction potential under short photoperiod. Nitrogen (N) is a main component of many metabolites that are involved in central processes in plants, and is therefore a major factor governing plant development and structure. We lack information about the influence of N nutrition on medical cannabis functional-physiology and development, and plant N requirements are yet unknown. The present study therefore investigated the developmental, physiological, and chemical responses of medical cannabis plants to N supply (30, 80, 160, 240, and 320 mgL−1 N) under long photoperiod. The plants were cultivated in an environmentally controlled growing room, in pots filled with soilless media. We report that the morpho-physiological function under long photoperiod in medical cannabis is optimal at 160 mgL−1 N supply, and significantly lower under 30 mgL−1 N, with visual deficiency symptoms, and 75 and 25% reduction in plant biomass and photosynthesis rate, respectively. Nitrogen use efficiency (NUE) decreased with increasing N supply, while osmotic potential, water use efficiency, photosynthetic pigments, and total N and N-NO3 concentrations in plant tissues increased with N supply. The plant ionome was considerably affected by N supply. Concentrations of K, P, Ca, Mg, and Fe in the plant were highest under the optimal N level of 160 mgL−1 N, with differences between organs in the extent of nutrient accumulation. The majority of the nutrients tested, including P, Zn, Mn, Fe, and Cu, tended to accumulate in the roots > leaves > stem, while K and Na tended to accumulate in the stem > leaves > roots, and total N, Ca, and Mg accumulated in leaves > roots > stem. Taken together, the results demonstrate that the optimal N level for plant development and function at the vegetative growth phase is 160 mgL−1 N. Growth retardation under lower N supply (30–80 mgL−1) results from restricted availability of photosynthetic pigments, carbon fixation, and impaired water relations. Excess uptake of N under supply higher than 160 mgL−1 N, promoted physiological and developmental restrictions, by ion-specific toxicity or indirect induced restrictions of carbon fixation and energy availability.

 

Citation

 

Saloner A, Bernstein N. Response of Medical Cannabis (Cannabis sativa L.) to Nitrogen Supply Under Long Photoperiod. Front Plant Sci. 2020 Nov 17;11:572293. doi: 10.3389/fpls.2020.572293. PMID: 33312185; PMCID: PMC7704455.

 

Full paper @ https://www.frontiersin.org/articles/10.3389/fpls.2020.572293/full

 

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Fusarium and Pythium species infecting roots of hydroponically grown marijuana (Cannabis sativa L.) plants

 

2018

 

Abstract

 

An increase in the cultivation of Cannabis sativa (cannabis or marijuana) plants in Canada is becoming associated with increased incidence and severity of various diseases, many of which have not been previously reported. In this study, hydroponically grown C. sativa plants were sampled over a 3-year period (2014–2017) to determine the prevalence of root pathogens. Following isolation, pathogenicity studies were conducted to establish the extent of disease symptoms caused by the recovered microbes. Root rot was found to be caused by two Pythium species – Pythium dissotocum Drechsler and P. myriotylum Drechsler. As well, two Fusarium species were recovered from diseased plants – Fusarium oxysporum Schlecht. emend. Snyder & Hansen and F. solani (Mart.) Sacc. Upon inoculation onto healthy plants, all isolates of Pythium spp. caused browning and a reduction in root mass, accompanied by stunting. Inoculation of plants with F. oxysporum caused browning of roots and crown rot infection, accompanied by pith and vascular discolouration, and in some cases wilting of plants, while root and crown infection was observed with F. solani. Phylogenetic analysis of internal transcribed spacer (ITS) and elongation factor 1α (EF-1α) sequences revealed that the Fusarium species affecting cannabis plants shared 99–100% sequence homology with isolates causing stem rot and wilt in other hosts, including cumin and tomato, suggesting they were not uniquely adapted to cannabis. The potential for spread of F. oxysporum through the hydroponic system was confirmed by its detection in the recirculating nutrient solution. Furthermore, rooted cuttings obtained from commercial propagators were found to harbour Fusarium root infection that resulted in subsequent stunting, yellowing and occasional death of plants. This demonstrates the potential for long-distance spread of the pathogen. The two Pythium species recovered from cannabis plants have an extremely broad host range and are not unique to this host. An additional species, P. aphanidermatum (Edson) Fitzp., was recovered from diseased plants grown under greenhouse conditions in 2018. The management of these root pathogens on C. sativa will require the evaluation and implementation of sanitization methods, biological control agents, and chemical products adapted from greenhouse vegetable production practices. The use of pathogen-free propagation materials and identification of potential sources of disease resistance should also become a priority.

 

Discussion

 

Cannabis plants grown under indoor conditions in a hydroponic system were found to be infected with either Pythium or Fusarium spp. and showed stunted growth, but no obvious symptoms of chlorosis or wilting were seen. Occasional chlorosis associated with Pythium infection was observed on plants at the vegetative growth stage (authors, unpublished observations). However, under greenhouse hydroponic conditions, P. aphanidermatum was observed to cause plant death. In regards to F. oxysporum, rooted cuttings initiated in rockwool blocks received from commercial propagators and maintained under hydroponic cultivation showed the early development of characteristic symptoms of damping-off and root root, i.e. stunted plants with dark green or yellow curled leaves, and root lesions especially at root tips. These symptoms were apparent on 1-week-old cuttings and 3–6-week-old plants. This suggests that early infection can cause above-ground symptoms on younger plants but may be difficult to detect when plants reach a larger size, either in vegetative growth or in the flowering period. However, visual inspection of the root systems should reveal root browning, which is relatively easy to do in the hydroponic system but more difficult for plants grown in soil.

 

Inoculation experiments confirmed the ability of the tested isolates of Pythium and Fusarium species to reduce root growth and cause root rot. Wilting symptoms on plants inoculated with F. oxysporum were only observed in soil, where uptake of the nutrient solution by diseased roots would be more difficult compared with infected plants grown in a hydroponic system. Therefore, symptoms on soil-grown plants are likely to be more visible than on hydroponically grown plants. However, when the infection levels were high in vegetatively propagated plants grown in rockwool substrate, the plants showed visible symptoms of stunting, yellowing and curling of leaves, and root browning and damping-off during hydroponic cultivation at an early age. Artificial inoculation with F. solani resulted in infection of the crown tissues in soil-grown plants, and only root rot symptoms were observed on hydroponically grown plants. This species was isolated from diseased roots with <10% frequency, suggesting that it is not as prevalent as F. oxysporum, although it appears to be comparatively more damaging to roots.

 

Phylogenetic analysis using the ITS and EF-1α regions revealed that the Fusarium species affecting cannabis plants were grouped with other isolates originating from a range of hosts and were not unique to cannabis. Previously, F. oxysporum and F. solani were reported to cause damping-off on hemp seedlings, while F. solani was reported to cause root rot on older plants and F. oxysporum caused a wilt disease (McPartland, 1996). The wilt pathogens were reported to be F. oxysporum f. sp. cannabis Noviello & W.C. Snyder and F. oxysporum f. sp. vasinfectum W.C. Snyder & N.H. Hans. (McPartland & Hillig, 2004). The former formae specialis was reported to have a restricted host range limited to Cannabis sativa while the latter infected a broad range of hosts, including cotton, soybeans, tobacco (McPartland & Hillig, 2004) and is a widespread pathogen of cotton in the USA (Cianchetta et al., 2015). The F. oxysporum isolates recovered in the present study were not grouped with either of the formae speciales previously reported to affect hemp, and based on the symptoms and relatedness to other F. oxysporum isolates, they are probably generalized root and crown rot pathogens.

 

In the phylogenetic analysis of the ITS region, F. oxysporum f. sp. cannabis was grouped with two other f. sp. (spinaceae and tracheiphilum), supporting a close similarity that was also previously reported in a study involving the nuclear ribosomal intergeneric spacer (IGS) region (O’Donnell et al., 2009). In the 1980s, F. oxysporum f. sp. cannabis was considered as a potential biocontrol pathogen to eliminate illicit growing of cannabis plants for drug purposes (Hildebrand & McCain, 1978; McCain & Noviello, 1985); however, a detailed analysis of its use as a bioherbicide concluded that it was not sufficiently aggressive (Charudattan, 2011). The extent of distribution of F. oxysporum f. sp. cannabis and its host range are presently unknown due to the limited number of isolates available for study. Fusarium oxysporum contains a large number of formae speciales (Michielse & Rep, 2009), which were originally described to reflect host range specialization (Snyder & Hansen, 1940). While the f. sp. designations describe the pathogenic specialization within the species, they are not part of the formal taxonomic hierarchy (Kistler, 1997). Although comparisons of the EF-1α gene sequences distinguished among some formae speciales in this study, further studies of the host range of the isolates from cannabis in this study are needed. O’Donnell et al. (2009) reported that formae speciales of Fusarium are not always restricted to a specific range of hosts, and cross-infection between hosts can occur. Therefore, strains from cannabis are likely able to infect other hosts, and vice versa.

 

The three species of Pythium recovered from cannabis plants in this study have a wide host range, including many horticultural and field crops worldwide, e.g. beans, cilantro, opium, spinach, strawberry, soybean and tobacco (McCarter & Littrell, 1970; Watanabe, 1977; Kageyama & Ui, 1983; Bates & Stanghellini, 1984; Alam et al., 1996; Fortnum et al., 2000; Watanabe & Tojo, 2006; Corrêa et al., 2011; Romero et al., 2012; Tomioka et al., 2013; Rojas et al., 2017). Pythium root rot is also destructive on various crops grown in hydroponic systems, including lettuce, cucumber, tomato, sweet pepper and roses (Stanghellini & Kronland, 1986; Sutton et al., 2006). Previously, P. aphanidermatum and P. ultimum were reported to cause damping-off on hemp seedlings (McPartland, 1996), while P. aphanidermatum was recently reported to cause crown and root rot on field-grown hemp (Beckerman et al., 2017) and cannabis plants (Punja et al., 2018). Neither of P. dissotocum or P. myriotylum isolated in this study have been previously reported to infect cannabis plants. Pythium dissotocum Drechsler is capable of rapid growth at temperatures of 24–32°C and can infect via zoospores or mycelium (Van der Plaats-Niterink, 1981; Sutton et al., 2006). Similarly, P. myriotylum grows best at 25–30°C and can produce zoospores within this temperature range. Cannabis plants are generally grown at 24–27°C, which is within the range for growth of both Pythium species. Additionally, hydroponic cultivation may promote spread of Fusarium and Pythium pathogens, which are commonly encountered on other hydroponically grown horticultural crops (Sutton et al., 2006). While the overall infection level was around 1% of plants at later stages of production, once established, these pathogens can persist and spread in the recirculated hydroponic solution (Menzies & Bélanger, 1996). The most important initial sources of inoculum include infected rooted cuttings and propagation media, as well as potential hydroponic pipes and tubing, tools and equipment, and water (Sutton et al., 2006). Movement of infected rooted cuttings by propagators from one region of Canada to another can be an important source of Fusarium spread. Currently, there are no restrictions on the movement of propagation materials of cannabis as long as they are between licensed producers. The severity of the symptoms observed on 2–3-week-old plants suggested that a large proportion of the plants were infected early during propagation. The sporulation of F. oxysporum observed on crown tissues in this study suggests that airborne spread is likely to occur, as has been observed with F. oxysporum causing wilt and crown rot of tomato, basil and cucumber plants (Rowe et al., 1977; Gamliel et al., 1996; Katan et al., 1997; Rekah et al., 2000; Scarlett et al., 2015). Colonies of F. oxysporum were detected on Petri dishes left exposed in the growing environment, confirming the possibility of airborne spread of inoculum (authors, unpublished). Rooted plants produced by commercial propagators that are infected with Fusarium are a potentially important means of pathogen spread and should be monitored.

 

With the current expansion of the cannabis industry in Canada, additional research on the epidemiology and management of cannabis diseases is warranted. Furthermore, the efficacy of biological control products and reduced-risk chemicals for root disease management on cannabis needs to be evaluated. At present, there are two biocontrol products registered in Canada for management of root diseases on cannabis – Rootshield WP (Trichoderma harzianum Rifai strain RRL-AG2) and Prestop WP (Gliocladium catenulatum strain J1446) for root-infecting pathogens (https://www.canada.ca/en/health-canada/services/drugs-medication/cannabis/licensed-producers/policies-directives-guidance-information-bulletins/testing-cannabis-medical-purposes-unauthorized-pest-control-products.html), while Actinovate SP (Streptomyces lydicus strain WYEC 10–8), which was previously registered for powdery mildew and botrytis control, has been withdrawn. Evaluation of additional biocontrol products that have shown to be effective against root diseases on other horticultural crops, including Rhapsody (Bacillus subtilis strain QST 713) (Punja et al., 2016) and Mycostop (Streptomyces griseoviridis strain K61) (Punja & Yip, 2003; Rose et al., 2003) is needed to identify additional non-fungicide options for disease management by cannabis producers. In addition, the efficacy of sanitation methods, such as ultraviolet light, ozonation, chlorination, hydrogen peroxide, heat pasteurization and/or mechanical filtration for reducing inoculum presence in greenhouse production should be evaluated.

 

Citation

 

Zamir K. Punja & Gina Rodriguez (2018) Fusarium and Pythium species infecting roots of hydroponically grown marijuana (Cannabis sativa L.) plants, Canadian Journal of Plant Pathology, 40:4, 498-513, DOI: 10.1080/07060661.2018.1535466

 

Full text available https://www.tandfonline.com/doi/full/10.1080/07060661.2018.1535466

 

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Photoperiodic Response of In Vitro Cannabis sativa Plants

 

2020

 

Abstract

 

The majority of commercial Cannabis sativa L. (cannabis) cultivators use a 12.0-hour uninterrupted dark period to induce flowering; however, scientific information to prove this is the optimal dark period for all genotypes is lacking. Knowing genotype-specific photoperiods may help to promote growth by providing the optimal photoperiod for photosynthesis. To determine whether the floral initiation of cannabis explants respond to varied photoperiods in vitro, explants were grown under one of six photoperiod treatments: 12.0, 13.2, 13.8, 14.4, 15.0, and 16.0 hours per day for 4 weeks. The percentage of flowering explants was highest under 12.0- and 13.2-hour treatments. There were no treatment effects on the fresh weight, final height, and growth index. Based on the results, it is recommended that an uninterrupted dark period of at least 10.8 hours (i.e., 13.2-hour photoperiod) be used to induce flowering for the ‘802’ genotype. In vitro flowering could provide a unique and high-throughput approach to study floral/seed development and secondary metabolism in cannabis under highly controlled conditions. Further research should determine if this response is the same on the whole-plant level.

 

Conclusion

 

The results of this study demonstrated that explants of cannabis genotype ‘802’ can be induced to flower when the photoperiod is 13.2 h or less per day or, more correctly, 10.8 h or more per day of uninterrupted dark period. The percentage of flowering explants is the best indicator for photoperiod determination tests among the other metrics such as times for the days to first, 25%, and 50% floral initiation because it provides a more accurate representation of how the explants respond under the different photoperiod treatments. The growth of explants is not a suitable method to determine the plant growth response to photoperiod because there was large variation in size and growth of explants generated from tissue culture. Future research should use whole plants to determine the critical photoperiod for flower initiation for this genotype. With further investigation, the use of tissue culture can be used by cultivators to save time and space to determine the specific photoperiods for their genotypes to help optimize production. Additionally, this research can help establish an in vitro system to study floral/seed development, develop in vitro breeding platforms, and investigate the regulation of secondary metabolism under highly controlled conditions.

 

Citation

 

Moher, M., Jones, M., & Zheng, Y. (2020). Photoperiodic Response of in vitro Cannabis sativa Plants. Hortscience, 1-6.

Online paper https://journals.ashs.org/hortsci/view/journals/hortsci/56/1/article-p108.xml#:~:text=The%20majority%20of%20commercial%20Cannabis,for%20all%20genotypes%20is%20lacking

 

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Cannabis lighting: Decreasing blue photon fraction increases yield but efficacy is more important for cost effective production of cannabinoids

 

 

March 2021

 

Abstract

 

LED technology facilitates a range of spectral quality, which can be used to optimize photosynthesis, plant shape and secondary metabolism. We conducted three studies to investigate the effect of blue photon fraction on yield and quality of medical hemp. Conditions were varied among studies to evaluate potential interactions with environment, but all environmental conditions other than the blue photon fraction were maintained constant among the five-chambers in each study. The photosynthetic photon flux density (PPFD, 400 to 700 nm) was rigorously maintained at the set point among treatments in each study by raising the fixtures. The lowest fraction of blue photons was 4% from HPS, and increased to 9.8, 10.4, 16, and 20% from LEDs. There was a consistent, linear, 12% decrease in yield in each study as the fraction of blue photons increased from 4 to 20%. Dry flower yield ranged from 500 to 750 g m-2. This resulted in a photon conversion efficacy of 0.22 to 0.36 grams dry flower mass yield per mole of photons. Yield was higher at a PPFD of 900 than at 750 μmol m-2 s-1. There was no effect of spectral quality on CBD or THC concentration. CBD and THC were 8% and 0.3% at harvest in trials one and two, and 12% and 0.5% in trial three. The CBD/THC ratio was about 25 to 1 in all treatments and studies. The efficacy of the fixtures ranged from 1.7 (HPS) to 2.5 μmol per joule (white+red LED). Yield under the white+red LED fixture (10.4% blue) was 4.6% lower than the HPS on a per unit area basis, but was 27% higher on a per dollar of electricity basis. These findings suggest that fixture efficacy and initial cost of the fixture are more important for return on investment than spectral distribution at high photon flux.

 

Citation

 

Westmoreland FM, Kusuma P, Bugbee B. Cannabis lighting: Decreasing blue photon fraction increases yield but efficacy is more important for cost effective production of cannabinoids. PLoS One. 2021 Mar 23;16(3):e0248988. doi: 10.1371/journal.pone.0248988. PMID: 33755709; PMCID: PMC7987162.

 

Online paper available @ https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0248988

 

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Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions

 

 

December 2008

 

 

Abstract

 

Effect of different photosynthetic photon flux densities (0, 500, 1000, 1500 and 2000 μmol m(-2)s(-1)), temperatures (20, 25, 30, 35 and 40 °C) and CO2 concentrations (250, 350, 450, 550, 650 and 750 μmol mol(-1)) on gas and water vapour exchange characteristics of Cannabis sativa L. were studied to determine the suitable and efficient environmental conditions for its indoor mass cultivation for pharmaceutical uses. The rate of photosynthesis (PN) and water use efficiency (WUE) of Cannabis sativa increased with photosynthetic photon flux densities (PPFD) at the lower temperatures (20-25 °C). At 30 °C, PN and WUE increased only up to 1500 μmol m(-2)s(-1) PPFD and decreased at higher light levels. The maximum rate of photosynthesis (PN max) was observed at 30 °C and under 1500 μmol m(-2)s(-1) PPFD. The rate of transpiration (E) responded positively to increased PPFD and temperature up to the highest levels tested (2000 μmol m(-2)s(-1) and 40 °C). Similar to E, leaf stomatal conductance (gs) also increased with PPFD irrespective of temperature. However, gs increased with temperature up to 30 °C only. Temperature above 30 °C had an adverse effect on gs in this species. Overall, high temperature and high PPFD showed an adverse effect on PN and WUE. A continuous decrease in intercellular CO2 concentration (Ci) and therefore, in the ratio of intercellular CO2 to ambient CO2 concentration (Ci/Ca) was observed with the increase in temperature and PPFD. However, the decrease was less pronounced at light intensities above 1500 μmol m(-2)s(-1). In view of these results, temperature and light optima for photosynthesis was concluded to be at 25-30 °C and ∼1500 μmol m(-2)s(-1) respectively. Furthermore, plants were also exposed to different concentrations of CO2 (250, 350, 450, 550, 650 and 750 μmol mol(-1)) under optimum PPFD and temperature conditions to assess their photosynthetic response. Rate of photosynthesis, WUE and Ci decreased by 50 %, 53 % and 10 % respectively, and Ci/Ca, E and gs increased by 25 %, 7 % and 3 % respectively when measurements were made at 250 μmol mol-1 as compared to ambient CO2 (350 μmol mol(-1)) level. Elevated CO2 concentration (750 μmol mol(-1)) suppressed E and gs ∼ 29% and 42% respectively, and stimulated PN, WUE and Ci by 50 %, 111 % and 115 % respectively as compared to ambient CO2 concentration. The study reveals that this species can be efficiently cultivated in the range of 25 to 30 °C and ∼1500 μmol m(-2)s(-1) PPFD. Furthermore, higher PN, WUE and nearly constant Ci/Ca ratio under elevated CO2 concentrations in C. sativa, reflects its potential for better survival, growth and productivity in drier and CO2 rich environment.

 

Conclusions

 

In view of our results, it is concluded that C. sativa can utilize a fairly high level of PPFD and temperature for its gas and water exchange processes, and can perform much better if grown at ~ 1500 μmol m-2 s-1 PPFD and around 25 to 30 oC temperature conditions. Furthermore, higher PN, WUE and nearly constant Ci/Ca ratio under elevated CO2 concentration, reflects its potential for improved growth and productivity in drier and CO2 rich environment.

 

Citation

 

Chandra S, Lata H, Khan IA, Elsohly MA. Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions. Physiol Mol Biol Plants. 2008 Oct;14(4):299-306. doi: 10.1007/s12298-008-0027-x. Epub 2009 Feb 26. PMID: 23572895; PMCID: PMC3550641.

 

Full text https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3550641/

 

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Photosynthetic response of Cannabis sativa L., an important medicinal plant, to elevated levels of CO2

 

2011

 

Abstract

 

The effect of elevated CO2 concentrations (545 and 700 μmol mol−1) on gas exchange and stomatal response of four high Δ9-THC yielding varieties of Cannabis sativa (HPM, K2, MX and W1) was studied to assess their response to the rising atmospheric CO2 concentration. In general, elevated CO2 concentration (700 μmol mol−1) significantly (p < 0.05) stimulated net photosynthesis (PN), water use efficiency (WUE) and internal CO2 concentration (Ci), and suppressed transpiration (E) and stomatal conductance (gs) as compared to the ambient CO2 concentration (390 μmol mol−1) in all the varieties whereas, the effect of 545 μmol mol−1 CO2 concentration was found insignificant (p < 0.05) on these parameters in most of the cases. No significant changes (p < 0.05) in the ratio of internal to the ambient CO2 concentration (Ci/Ca) was observed in these varieties under both the elevated CO2 concentrations (545 and 700 μmol mol−1). An average increase of about 48 %, 45 %, 44 % and 38 % in PN and, about 177 %, 157 %, 191 % and 182 % in WUE was observed due to elevated CO2 (700 μmol mol−1) as compared to ambient CO2 concentration in HPM, K2, MX and W1 varieties, respectively. The higher WUE under elevated CO2 conditions in Cannabis sativa, primarily because of decreased stomatal conductance and subsequently the transpiration rate, may enable this species to survive under expected harsh greenhouse effects including elevated CO2 concentration and drought conditions. The higher PN, WUE and nearly constant Ci/Ca ratio under elevated CO2 concentrations in this species reflect a close coordination between its stomatal and mesophyll functions.

 

Citation

 

Chandra S, Lata H, Khan IA, Elsohly MA. Photosynthetic response of Cannabis sativa L., an important medicinal plant, to elevated levels of CO2. Physiol Mol Biol Plants. 2011;17(3):291-295. doi:10.1007/s12298-011-0066-6

 

Online paper https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3550578/

 

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DKW basal salts improve micropropagation and callogenesis compared to MS basal salts in multiple commercial cultivars of Cannabis sativa

 

2020

 

Abstract

 

Micropropagation of Cannabis sativa is an emerging area for germplasm storage and large-scale production of clean plants. Existing protocols use a limited number of genotypes and are often not reproducible. Previous studies reported MS + 0.5 μM TDZ to be optimal for Cannabis nodal micropropagation, yet our preliminary studies using nodal explants suggested this media may not be optimal. It resulted in excessive callus formation, hyperhydricity, low multiplication rates, and high mortality rates. Following an initial screen of four commonly used basal salt mixtures (MS, B5, BABI, and DKW), we determined that DKW produced the healthiest plants. In a second experiment, the multiplication rate and canopy area of explants grown on MS + 0.5 μM TDZ and DKW + 0.5 μM TDZ were compared using five drug-type cultivars to determine if the preference for DKW was genotype-dependent. Four cultivars had significantly higher multiplication rates on DKW + 0.5 μM TDZ with the combined average being 1.5x higher than explants grown on MS + 0.5 μM TDZ. The canopy area was also significantly larger on DKW + 0.5 μM TDZ for four cultivars with the combined average being twice as large as the explants grown on MS + 0.5 μM TDZ. In the third experiment, callogenesis was compared using a range of 2,4-D concentrations (0-30 μM) on both MS and DKW and similarly, callus growth was superior on DKW. This study presents the largest comparison of basal salt compositions on the micropropagation of five commercially grown Cannabis cultivars to date.

 

Citation

 

Serena R.G. Page, Adrian S. Monthony, A. Maxwell P. Jones. (2020) DKW basal salts improve micropropagation and callogenesis compared to MS basal salts in multiple commercial cultivars of Cannabis sativa bioRxiv 2020.02.07.939181; doi: https://doi.org/10.1101/2020.02.07.939181

 

Full paper https://www.biorxiv.org/content/10.1101/2020.02.07.939181v2.full

 

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Widely assumed phenotypic associations in Cannabis sativa lack a shared genetic basis

 

 

2021

 

 

Abstract

 

The flowering plant Cannabis sativa, cultivated for centuries for multiple purposes, displays extensive variation in phenotypic traits in addition to its wide array of secondary metabolite production. Notably, Cannabis produces two well-known secondary-metabolite cannabinoids: cannabidiolic acid (CBDA) and delta-9-tetrahydrocannabinolic acid (THCA), which are the main products sought by consumers in the medical and recreational market. Cannabis has several suggested subspecies which have been shown to differ in chemistry, branching patterns, leaf morphology and other traits. In this study we obtained measurements related to phytochemistry, reproductive traits, growth architecture, and leaf morphology from 297 hybrid individuals from a cross between two diverse lineages. We explored correlations among these characteristics to inform our understanding of which traits may be causally associated. Many of the traits widely assumed to be strongly correlated did not show any relationship in this hybrid population. The current taxonomy and legal regulation within Cannabis is based on phenotypic and chemical characteristics. However, we find these traits are not associated when lineages are inter-crossed, which is a common breeding practice and forms the basis of most modern marijuana and hemp germplasms. Our results suggest naming conventions based on leaf morphology do not correspond to the chemical properties in plants with hybrid ancestry. Therefore, a new system for identifying variation within Cannabis is warranted that will provide reliable identifiers of the properties important for recreational and, especially, medical use.

 

Conclusions

 

The fact that most of the phenotypic traits are not genetically correlated has significant implications for both Cannabis breeders and commercial growers. If these traits are not linked, as previously thought, then it is possible to select for new combination of traits when breeding for novel varieties. This expands the possibility of generating varieties with a unique combination of traits providing unforeseen medicinal and industrial value. Future breeding can be done to maximize combinations of these traits.

 

Citation

 

Vergara D, Feathers C, Huscher EL, Holmes B, Haas JA, Kane NC. 2021. Widely assumed phenotypic associations in Cannabis sativa lack a shared genetic basis.

 

Full paper https://peerj.com/articles/10672/

 

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