Metabolomics-Driven Investigation of Harpin αβ and Laminarin Effects on Cannabis sativa L. Employing GC/EI/MS and 1H NMR Metabolomics

Hemp (Cannabis sativa L.) is a polymorphic species that synthesizes an array of bioactive metabolites, with cannabinoids and terpenoids constituting the major chemical classes. Until recently, the lack of legislative framework led to limited research on hemp’s plant protection and nutrition. Biostimulants have recently attracted scientific attention as sustainable alternatives to plant protection products (PPPs). Herein, we investigated the effects of biostimulant harpin (αβ) proteins and the PPP polysaccharide laminarin on hemp (cv. Futura 75), employing GC/EI/MS and 1H NMR metabolomics. Analyses demonstrated that treatments induced distinct shifts in the metabolism of the plants, thus, enabling the discovery of metabolite-biomarkers of physiological adaptation, defense mechanisms (α-linolenic acid), and bioactivity (cannabinoids). Harpin and laminarin altered the concentration of bioactive compounds such as cannabidiol, essential amino acids including L-phenylalanine and GABA, salicylate, and caffeate. Pathway analysis revealed treatment-specific modulation of key metabolic networks, with harpin triggering early, yet transient activation of phenylpropanoid- and amino acid-related pathways before broad repression, whereas laminarin maintained a more balanced regulation, sustaining defense-related biosynthesis while preserving core primary metabolism. Results advance the understanding of molecular mechanisms underlying biostimulants’ action in hemp and support their potential for improving plant health and attributes of cannabis-derived products, providing insights for its sustainable cultivation.