Supplementation of fertiliser with the biostimulant molasses enhances hemp (Cannabis sativa) seed functional food antioxidant capacity by induction of stress responses

Hemp is low-tetrahydrocannabinol (THC) Cannabis sativa that is cultivated globally for food and fibre. Hemp seeds and seed-oil are popularly consumed individually or utilised within cooking, due to their flavour, nutrition, and functional food benefits. The functional food properties of hemp seed include its beneficial fatty acid (FA) profile and antioxidant activity, which are associated with reduced inflammation that benefits chronic conditions including cardiovascular disease and cancer. Maximising these functional food properties can offer extensive health benefits. Biostimulants – such as molasses – are fertiliser additives that are associated with improvements to plant growth, yield, and biochemical composition; however, they have been scarcely applied to hemp. Furthermore, due to the complex composition of biostimulants, understanding their modes of action poses a significant challenge, impeding the optimization of their usage and the realization of associated benefits. Accordingly, this study aimed to characterise the impact of molasses on the functional food properties of hemp seeds and explore biostimulant-induced biochemical changes as indicators of modes of effect. Although molasses treatment did not significantly alter the FA profile (p = 0.960 for ω-6:ω-3 FA ratio), the antioxidant capacity (as measured by ABTS) was significantly increased (3.8-fold increase, p = 0.008). Metabolite profiling and statistical modelling indicated that this change was likely associated with increases in several lipophilic antioxidant metabolites, including hydroxycinnamic acid amides and cannabisins. Comparison of root, leaf, seed, and sugar leaf tissue changes in phytohormones and metabolites indicated that the growth of hemp with molasses was predominantly associated with the induction of the plant's endogenous stress response within the roots. These results indicate that the biostimulant molasses is a beneficial fertiliser additive for enhancing the functional food (antioxidant) potential of hemp seeds, thereby improving the health-benefits imparted to consumers.