Researchers from the Graduate University of Advanced Technology in Iran report in a new study that a combined treatment of melatonin and zinc oxide nanoparticles can significantly improve growth, stress tolerance, nutrient uptake, and cannabinoid production in Cannabis sativa.
The study, published in the journal Plant Nano Biology, is titled Synergistic Effects of Melatonin and Zinc Oxide Nanoparticles on Oxidative Stress Mitigation, Nutrient Accumulation, and Secondary Metabolite Enhancement in Cannabis sativa L.
The researchers tested melatonin alongside zinc oxide nanoparticles at concentrations of 5 and 10 parts per million, both individually and in combination. While zinc oxide nanoparticles emerged as the primary driver of growth-related improvements, melatonin played a key role in reducing oxidative stress and selectively influencing secondary metabolites. Plants receiving the combined treatment showed higher shoot and root biomass, improved water retention, stronger membrane stability, and increased photosynthetic pigments compared to untreated controls.
Measures of oxidative stress, including hydrogen peroxide and malondialdehyde, were substantially lower in treated plants. The most pronounced reductions were observed when melatonin was paired with zinc oxide nanoparticles, indicating an additive protective effect against cellular damage. These improvements in stress regulation coincided with marked increases in secondary metabolites, including flavonoids, phenolics, alkaloids, cannabidiol, and tetrahydrocannabinol.
Zinc oxide nanoparticles were especially effective at increasing cannabinoid levels, with cannabidiol rising by more than 120% at the highest concentration tested. Melatonin alone reduced tetrahydrocannabinol levels while increasing cannabidiol, suggesting a selective influence on cannabinoid biosynthesis. The treatments also enhanced the accumulation of essential nutrients such as potassium, magnesium, iron, manganese, and zinc, further supporting overall plant performance.
Researchers conclude the study by stating:
The combination of melatonin and ZnO-NPs enhances Cannabis sativa growth, stress tolerance, nutrient accumulation, and secondary metabolite production. While ZnO-NPs alone strongly drive growth and metabolic improvements, melatonin primarily contributes to oxidative stress mitigation and selective metabolite regulation. Combined treatments exhibit additive or modestly synergistic effects, particularly in root development, oxidative stress markers, and nutrient uptake. These findings highlight the potential of integrating nanoparticles and phytohormones as a practical strategy for improving hemp cultivation, supporting applications in the pharmaceutical, nutraceutical, and cosmetic industries. Further studies are warranted to optimize concentrations, application methods, and the molecular understanding of cannabinoid biosynthesis modulation.
