Water-deficit stress is typically viewed as detrimental to agricultural yields. It has been found to enhance secondary metabolite concentrations in certain essential oil-producing plants, including Cannabis sativa L. Cannabis is a versatile plant from the Cannabaceae family which is used for its fibers, seeds, and bioactive compounds, including medicinal and recreational cannabinoids. Furthermore, it exhibits significant metabolic shifts under water-deficit stress conditions, which may impact the production of these resources. This review explores the physiological mechanisms underlying the metabolic responses of cannabis to water-deficit stress, focusing on how water-deficit stress could promote the accumulation of secondary metabolites. Water-deficit stress induces metabolic changes in cannabis, leading to secondary metabolite accumulation. Water shortages cause stomatal closure, significantly reducing CO₂ uptake and fixation via the Calvin cycle and leading to an oversupply of NADPH+H⁺. This oversupply allows metabolic processes to shift toward synthesizing highly reduced compounds, such as secondary metabolites. Overall, the literature suggests that the controlled application of water-deficit stress during cannabis cultivation can enhance cannabinoid quality and yields, offering a practical strategy for optimizing plant productivity while addressing current knowledge gaps in metabolic signaling pathways.

Jasmonates have emerged as a prominent elicitor for enhancing trichome development and cannabinoid production in Cannabis sativa L. (cannabis). These glandular trichomes synthesize and store important cannabinoids, including tetrahydrocannabinol (THC) and cannabidiol (CBD), which determine the yield, potency, and quality of cannabis flowers. Methyl jasmonate (MeJA) acts through the COI1–JAZ–MYC signaling pathway to upregulate genes associated with trichome initiation and cannabinoid precursor formation. Evidence suggests that moderate MeJA concentrations (typically 50–100 µM) can effectively boost trichome density, elevate hexanoyl-CoA availability, and modestly enhance key biosynthetic enzyme activities, ultimately increasing THC and CBD content. However, higher methyl jasmonate doses can amplify these benefits, yet pose a risk of excessive vegetative stunting, highlighting the crucial trade-off between enhancing cannabinoid potency and maintaining overall biomass yield. Interaction with hormones like gibberellins, salicylic acid, and ethylene further shapes the plant’s stress responses and secondary metabolism. Application in controlled environments, such as greenhouses or vertical farms, shows promise for enhancing resin production while minimizing biomass loss. In outdoor conditions, the application may offer additional defense benefits against pests and pathogens. These responses can vary depending on the cultivar, underscoring the importance of cultivar-specific optimization. As demand for high-cannabinoid cannabis products continues to grow and agrochemical options remain limited, leveraging MeJA treatments offers a practical, non-genetically modified approach to optimize yield, quality, and resilience in cannabis cultivation.

Trichomes in cannabis (Cannabis sativa L.) are specialized structures responsible for cannabinoid and terpene biosynthesis, making their density a critical parameter for both research and industrial applications. However, consistent trichome density assessment remains challenging due to anatomical variability and the absence of standardized methodologies. This review critically examines the existing literature on trichome quantification across key floral structures—such as bracts, sugar leaves, calyxes, and the main cola—to identify the most reliable sites and practices for accurate evaluation. Evidence suggests that bracts represent the most consistent sampling unit, given their homogeneous trichome distribution and elevated cannabinoid concentration. Whilst sugar leaves and calyxes are also frequently analyzed, their morphological variability requires cautious interpretation. Furthermore, trichome shape, size, maturity, and vegetal surface expansion/shrinkage during stress must be considered when correlating density with secondary metabolite production. We also highlight the advantages of using more than only one floral structure and integrating microscopic imaging and software-assisted analysis to enhance reproducibility and accuracy. By synthesizing current methodologies and proposing pathways for standardization, this review aims to support more robust trichome assessment protocols, ultimately improving cannabinoid yield optimization, quality control, broader cannabis research frameworks, and an important aesthetic parameter for consumers. Future research efforts should focus on advancing imaging methodologies and optimizing sampling protocols to further improve the precision and reproducibility of trichome density and cannabinoid analyses.

Water-deficit stress is typically viewed as detrimental to agricultural yields. It has been found to enhance secondary metabolite concentrations in certain essential oil-producing plants, including Cannabis sativa L. Cannabis is a versatile plant from the Cannabaceae family used for its fibers, seeds, and bioactive compounds, including medicinal and recreational cannabinoids. Furthermore, it exhibits significant metabolic shifts under water-deficit stress conditions, which may impact the production of these resources. This review explores the physiological mechanisms underlying the metabolic responses of cannabis to water-deficit stress, focusing on how water-deficit stress could promote the accumulation of secondary metabolites. Water-deficit stress induces metabolic changes in cannabis, leading to secondary metabolite accumulation. Water shortage causes stomatal closure, significantly reducing CO2 uptake and fixation via the Calvin cycle, leading to an oversupply of NADPH+H+. This oversupply allows metabolic processes to shift toward synthesizing highly reduced compounds, such as secondary metabolites. Overall, the literature suggests that the controlled application of water-deficit stress during cannabis cultivation can enhance cannabinoid quality and yield, offering a practical strategy for optimizing plant productivity while addressing current knowledge gaps in metabolic signaling pathways.

As high-CBD cannabis (Cannabis sativa L.) gains legal and commercial relevance in the United States, studies evaluating how external inputs impact critical traits remain limited. This study investigates the effects of methyl jasmonate (MeJA), ammonium bicarbonate (AB), and the genetic source (mother plant identity) on the growth and secondary metabolite traits of indoor cannabis. Plants were treated with 1 mM MeJA and/or AB under controlled conditions, and key traits, such as plant height, chlorophyll content, biomass, trichome density, and cannabinoid concentration, were measured. The MeJA treatment led to a significant 32% increase in trichome density. However, it did not significantly alter CBD or THC concentrations. The AB treatment enhanced vegetative growth, increasing chlorophyll content and plant height while reducing CBD concentrations, but the biomass gains could compensate for the lower cannabinoid in the total production. An interaction between MeJA and AB altered the CBD content, suggesting that MeJA may mitigate AB’s negative effect on cannabinoid synthesis. The genetic source significantly influenced most of the measured traits, highlighting the role of the genotype in trait expression and the importance of clonal consistency. These findings highlight the complex dynamics of external inputs and genetic factors in cannabis production, emphasizing the need for further research to optimize cultivation strategies. Future studies should refine input combinations and doses to improve both yield and cannabinoid profiles.

Trichomes in Cannabis sativa are specialized structures responsible for cannabinoid and terpene biosynthesis, making their density a critical factor for both research and industrial applications. Despite their importance, trichome density analysis is hindered by variability across plant structures and the lack of standardized protocols. This study evaluates different plant structures—bracts, sugar leaves, calyxes, and the main cola—to determine the most reliable site for trichome counting. Among these, bracts emerge as the most consistent due to their homogeneous trichome distribution and high cannabinoid concentration. While sugar leaves and calyxes also contribute to trichome yield assessments, their variability necessitates careful sampling. Moreover, trichome shape and size must be taken into consideration when correlating trichome density with secondary metabolite levels. The integration of microscopic imaging and software-assisted counting enhances accuracy and reproducibility in trichome density analysis. Establishing a standardized protocol for trichome assessment will improve cannabinoid yield optimization, quality control, and overall Cannabis research methodologies. Incorporating morphological data (trichome density, distribution, shape, and size) with chemical assays (cannabinoid and terpene identification and quantification) thus provides a more robust assessment of Cannabis potency and value. Future work should refine imaging techniques and sampling strategies to further enhance trichome analysis reliability.