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.

Agroecosystem and ecological cycling loops are open when considering the reutilization of inputs applied in farming areas. Non-renewable resources have been transformed or relocated from the air, water and land into the system and are flowing out as wastes rather than reusable, recyclable resources. This current environmental situation is promoting the development of methods able to optimize nutrient cycling, minimize use of external inputs, and maximize input use efficiency. Some humic products are derived from lignin found in wheat straw and biofertilizers as compost and manure teas can be made using residues. Also, these biostimulants might decrease the necessity of synthetic inputs. This review strives to enhance our understanding of the conjunctive use of humic substances (HS) and biofertilizers. The biostimulant effects of each of these compounds are shown in the literature. Thus, our review question is whether the combined application of HS and biofertilizers can promote synergy between both compounds and potentially more efficacy. The effects promoted by using HS plus biofertilizers on plants and microorganisms are very interconnected, so sometimes these effects can be confounded. For instance, the root elongation promoted by HS might increase hyphal fungi colonization. Therefore, this review as divided in three sections: Responses of plants, fungi and bacteria. The findings indicate that the source and application rate of HS will have a strong impact on whether plant growth and microbial activity significantly improved. The microbial species and plant type also influence the response to HS. The prospects of the conjunctive use of and biofertilizers to stimulate plant development and microbial activity in agricultural systems are theoretically substantial when considering the total number of studies included in this review.

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.