Moving Away from 12:12; the Effect of Different Photoperiods on Biomass Yield and Cannabinoids in Medicinal Cannabis

An In Vitro Phytohormone Survey Reveals Concerted Regulation of the Cannabis Glandular Trichome Disc Cell Proteome

Cannabis (Cannabis sativa L.) flower glandular trichomes (GTs) are the main site of cannabinoid synthesis. Phytohormones, such as jasmonic acid (JA) and salicylic acid (SA), have been shown to increase cannabinoid content in cannabis flowers, but how this is regulated remains unknown. This study aimed to understand which biological processes in GT disc cells phytohormones control by using an in vitro assay. Live GT disc cells were isolated from a high-tetrahydrocannabinol cannabis cultivar and incubated on basal media plates supplemented with either kinetin (KIN), JA, SA, abscisic acid, ethephon, gibberellic acid, brassinolide, or sodium diethyldithiocarbamate. Quantitative proteomic analysis revealed that KIN, JA, and SA caused the greatest number of changes in the GT disc cell proteome. Surprisingly, none of the treatments concertedly increased cannabinoid content or the abundance of related biosynthetic proteins in the GT, suggesting that cannabinoid increases in previous in planta phytohormone studies are likely due to other processes, such as increased GT density. As well, KIN-, JA-, and SA-treated GTs had numerous differentially abundant proteins in common. Several were key proteins for leucoplast differentiation, cuticular wax and fatty acid metabolism, and primary metabolism regulation, denoting that cytokinin, JA, and SA signalling are likely important for coordinating cannabis GT differentiation and development.

Same, yet different: towards understanding nutrient use in hemp- and drug-type Cannabis

Cannabis sativa L., one of the oldest cultivated crops, has a complex domestication history due to its diverse uses for fibre, seed, oil, and drugs, and its wide geographic distribution. This review explores how human selection has shaped the biology of hemp and drug-type Cannabis, focusing on acquisition and utilization of nitrogen and phosphorus, and how resulting changes in source-sink relations shape their contrasting phenology. Hemp has been optimized for rapid, slender growth and nutrient efficiency, whereas drug-type cultivars have been selected for compact growth with large phytocannabinoid-producing female inflorescences. Understanding these nutrient use and ontogenetic differences will enhance our general understanding of resource allocation in plants. Knowledge gained in comparison with other model species, such as tomato, rice, or Arabidopsis can help inform crop improvement and sustainability in the cannabis industry.

Optimized guidelines for feminized seed production in high-THC Cannabis cultivars

With the partial legalization of high-THC Cannabis sativa across 23 states for recreational use and 38 states for medical purposes in the United States, the Cannabis industry is poised for significant growth. Projected to reach a sales volume of $50.7 billion by 2028, this growth is driven by the trend of lifting Cannabis prohibition. High-THC C. sativa cultivars, containing more than 0.3% delta-9 tetrahydrocannabinol (Δ9-THC) as defined by the 2018 US Farm Bill, are used for both medicinal and recreational purposes. Cannabis sativa is a short day, dioecious, annual plant, where female plants are favored for THC production, which requires seed feminization techniques to ensure an accurate female plant population. This involves using an ethylene inhibitor to induce sex reversal, leading to male flower development on female plants, allowing for self-pollination and the production of feminized seeds. However, challenges such as seed viability and the occurrence of male flowers in progeny have been noted. This review provides guidelines to enhance the production of viable feminized seeds in high-THC Cannabis cultivars. Literature findings indicate that Silver Thiosulfate (STS) is the most effective ethylene inhibitor for sex reversal and seed feminization in high-THC Cannabis cultivars. Specifically, a single dose of 3 mM STS should be applied during the vegetative stage via foliar spraying until runoff, followed by exposure to a short photoperiod of up to 12 hours to induce flowering and seed production. Progeny plants should be assessed for seed germination rate and compared for growth performance with the original parent plant to assess the declining effects of inbreeding. Adhering to these guidelines can improve the quality and viability of feminized seeds, meeting commercial market standards and industry demands for high-THC Cannabis cultivars.

Cannabis-Based Phytocannabinoids: Overview, Mechanism of Action, Therapeutic Application, Production, and Affecting Environmental Factors

This review provides an overview of cannabis-based phytocannabinoids, focusing on their mechanisms of action, therapeutic applications, and production processes, along with the environmental factors that affect their quality and efficacy. Phytocannabinoids such as THC (∆9-tetrahydrocannabinol), CBD (cannabidiol), CBG (cannabigerol), CBN (cannabinol), and CBC (cannabichromene) exhibit significant therapeutic potential in treating various physical and mental health conditions, including chronic pain, epilepsy, neurodegenerative diseases, skin disorders, and anxiety. The cultivation of cannabis plays a crucial role in determining cannabinoid profiles, with indoor cultivation offering more control and consistency than outdoor methods. Environmental factors such as light, water, temperature, humidity, nutrient management, CO2, and the drying method used are key to optimizing cannabinoid content in inflorescences. This review outlines the need for broader data transfer between the health industry and technological production, especially in terms of what concentration and cannabinoid ratios are effective in treatment. Such data transfer would provide cultivators with information on what environmental parameters should be manipulated to obtain the required final product.

Illuminating Cannabis sativa L.: The Power of Light in Enhancing C. sativa Growth and Secondary Metabolite Production

Light is crucial for higher plants, driving photosynthesis and serving as a powerful sensory signal that profoundly modulates growth, development, physiological functions, hormone activation, and biochemical pathways. Various light parameters-quality, intensity, composition, and photoperiod-exert a tremendous influence on plant growth and development, particularly in industrial hemp (Cannabis sativa L.). C. sativa, a crop of historical significance and unparalleled versatility, holds immense value in the food, fiber, and medicinal industries. The cultivation of medicinal cannabis is burgeoning in controlled environments due to evolving healthcare regulations. Optimal light conditions significantly enhance both yield and harvest quality, notably increasing the density of apical inflorescences and the ratio of inflorescence to total aboveground biomass. C. sativa metabolites, especially phenolic and terpene compounds and Phytocannabinoids like CBD (cannabidiol), THC (tetrahydrocannabinol), and CBG (cannabigerol), possess immense medicinal value. Secondary metabolites in C. sativa predominantly accumulate in the trichomes of female flowers and surrounding sugar leaves, underscoring the critical need to boost inflorescence weight and metabolite concentrations while ensuring product consistency. Different light parameters distinctly impact C. sativa's metabolic profile, providing a robust foundation for understanding the optimal conditions for synthesizing specific secondary metabolites. While the effects of light measurement on various crops are well-established, scientific evidence specifically relating to light quality effects on C. sativa morphology and secondary metabolite accumulation remains scarce. In this review, we critically summarized how different light properties can alter cannabis growth (vegetative and reproductive), physiology and metabolism. Furthermore, the mechanisms by which specific wavelengths influence growth, development, and secondary metabolite biosynthesis in C. sativa are not fully elucidated, which could be a prospective task for future researchers. Our review paves the way for a profound understanding of light's influence on C. sativa growth and advancements in greenhouse settings to maximize metabolite production for commercial use.

Effect of Hemp Extraction Procedures on Cannabinoid and Terpenoid Composition

A variety of techniques have been developed to extract hemp phytochemicals for research and consumption. Some of the most common processes in the industry include supercritical CO2 extraction, hydrodistillation, and solvent-based (ethanol) extractions. Each of these processes has the potential to differentially extract various phytochemicals, which would impact their efficacy, tolerability, and safety. However, despite these differences, there has been no direct comparison of the methods and the resulting phytochemical composition. This work aimed to compare cannabinoid and terpene profiles using the three primary commercial procedures, using hemp inflorescence from a CBD/CBG dominant Cannabis sativa L. cultivar. Extracts were then evaluated for their terpene and cannabinoid content using GC-MS and LC-MS/MS, respectively. Hydrodistilled extracts contained the most variety and abundance of terpenes with β-caryophyllene to be the most concentrated terpene (25-42 mg/g). Supercritical CO2 extracts displayed a minimal variety of terpenes, but the most variety and abundance of cannabinoids with CBD ranging from 12.8-20.6 mg/g. Ethanol extracts contained the most acidic cannabinoids with 3.2-4.1 mg/g of CBDA along with minor terpene levels. The resulting extracts demonstrated substantially different chemical profiles and highlight how the process used to extract hemp can play a large role in product composition and potential biological effects.

Ménage à trois: light, terpenoids, and quality of plants

In controlled environment agriculture (CEA), light is used to impact terpenoid production and improve plant quality. In this review we discuss various aspects of light as important regulators of terpenoid production in different plant organs. Spectral quality primarily modifies terpenoid profiles, while intensity and photoperiod influence abundances. The central regulator of light signal transduction elongated hypocotyl 5 (HY5) controls transcriptional regulation of terpenoids under UV, red (R), and blue (B) light. The larger the fraction of R and green (G) light, the more beneficial the effect on monoterpenoid and sesquiterpenoid biosynthesis, and such an effect may depend on the presence of B light. A large fraction of R light is mostly detrimental to tetraterpenoid production. We conclude that light is a promising tool to steer terpenoid production and potentially tailor the quality of plants.

Longer Photoperiod Substantially Increases Indoor-Grown Cannabis' Yield and Quality: A Study of Two High-THC Cultivars Grown under 12 h vs. 13 h Days

Indoor-grown Cannabis sativa is commonly transitioned to a 12 h daily photoperiod to promote flowering. However, our previous research has shown that some indoor-grown cannabis cultivars can initiate strong flowering responses under daily photoperiods longer than 12 h. Since longer photoperiods inherently provide higher daily light integrals (DLIs), they may also increase growth and yield. To test this hypothesis, two THC-dominant cannabis cultivars, 'Incredible Milk' (IM) and 'Gorilla Glue' (GG), were grown to commercial maturity at a canopy level PPFD of 540 µmol·m-2·s-1 from white LEDS under 12 h or 13 h daily photoperiods, resulting in DLIs of 23.8 and 25.7 mol·m-2·d-1, respectively. Both treatments were harvested when the plants in the 12 h treatment reached maturity according to established commercial protocols. There was no delay in flowering initiation time in GG, but flowering initiation in IM was delayed by about 1.5 d under 13 h. Stigma browning and trichome ambering also occurred earlier and progressed faster in the 12 h treatment in both cultivars. The vegetative growth of IM plants in the 13 h treatment was greater and more robust. The inflorescence yields were strikingly higher in the 13 h vs. 12 h treatment, i.e., 1.35 times and 1.50 times higher in IM and GG, respectively, which is 4 to 6 times higher than the relative increase in DLIs. The inflorescence concentrations of major cannabinoids in the 13 h treatment were either higher or not different from the 12 h treatment in both cultivars. These results suggest that there may be substantial commercial benefits for using photoperiods longer than 12 h for increasing inflorescence yields without decreasing cannabinoid concentrations in some cannabis cultivars grown in indoor environments.

Comparative genomics of flowering behavior in Cannabis sativa

Cannabis sativa L. is a phenotypically diverse and multi-use plant used in the production of fiber, seed, oils, and a class of specialized metabolites known as phytocannabinoids. The last decade has seen a rapid increase in the licit cultivation and processing of C. sativa for medical end-use. Medical morphotypes produce highly branched compact inflorescences which support a high density of glandular trichomes, specialized epidermal hair-like structures that are the site of phytocannabinoid biosynthesis and accumulation. While there is a focus on the regulation of phytocannabinoid pathways, the genetic determinants that govern flowering time and inflorescence structure in C. sativa are less well-defined but equally important. Understanding the molecular mechanisms that underly flowering behavior is key to maximizing phytocannabinoid production. The genetic basis of flowering regulation in C. sativa has been examined using genome-wide association studies, quantitative trait loci mapping and selection analysis, although the lack of a consistent reference genome has confounded attempts to directly compare candidate loci. Here we review the existing knowledge of flowering time control in C. sativa, and, using a common reference genome, we generate an integrated map. The co-location of known and putative flowering time loci within this resource will be essential to improve the understanding of C. sativa phenology.

Is Twelve Hours Really the Optimum Photoperiod for Promoting Flowering in Indoor-Grown Cultivars of Cannabis sativa?

Cannabis sativa ("cannabis" hereafter) is a valuable recent addition to Canada's economy with the legalization for recreational use in 2018. The vast majority of indoor cannabis cultivators use a 12-h light/12-h dark photoperiod to promote flowering. To test the hypothesis that robust flowering initiation responses can be promoted in indoor-grown cannabis cultivars under longer photoperiods, clones of ten drug-type cannabis cultivars were grown under six photoperiod treatments. All treatments were based on a standard 24-h day and included 12 h, 12.5 h, 13 h, 13.5 h, 14 h, and 15 h of light. The plants were grown in a growth chamber for 3 to 4 weeks, receiving an approximate light intensity of 360 µmol·m^-2·s^-1 from white LEDs. Flowering initiation, defined as the appearance of ≥3 pairs of stigmas at the apex of the primary shoot, occurred in all cultivars under all photoperiod treatments up to 14 h. Delays in flowering initiation time under 14 h vs. 12 h ranged from no delay to approximately 4 days, depending on the cultivar. Some cultivars also initiated flowering under 15 h, but floral tissues did not further develop beyond the initiation phase. Harvest metrics of some cultivars responded quadratically with increasing photoperiod, with ideal levels of key flowering parameters varying between 12 h and 13 h. These results suggest there is potential to increase yield in some indoor-grown cannabis cultivars by using longer than 12-h photoperiods during the flowering stage of production. This is attributed to the inherently higher daily light integrals. Indoor cannabis growers should investigate the photoperiod responses of their individual cultivars to determine the optimal photoperiod for producing floral biomass.