Enhancement of the production of terpenoid and flavonoid secondary metabolites in the ground and aerial parts of licorice composite plant in a hydroponic system

Hairy roots mediated by Agrobacterium rhizogenes can be obtained from the composite plants (plants with hairy roots and untransformed aerial parts) by ex vitro method. Composite plants can produce higher amounts of secondary metabolites by merging hydroponic systems. This provides a stable condition for composite plants, in which various metabolites are produced in different parts. In the present study, composite plants of Glycyrrhiza glabra were produced under ex vitro conditions and transferred into a hydroponic culture medium to produce and extract secondary metabolites. The results showed a 4.8- and 1.8-fold enhancement in the expressions of SQS1 and bAS genes in the roots of the composite plants compared to the control group, respectively. The levels of glycyrrhizin (1.7) and glabridin (3.5) were higher in the leaves of the composite plants compared to the controls. Moreover, higher amounts of glabridin (1.7) were observed in the roots of the composite plants compared to the control group. Investigation of the oxidative enzymes in the composite plants and control group revealed that the plants used more secondary metabolites through Agrobacterium inoculation. The plants needed more antioxidant enzymes to counter the release of oxygen-free radicals in control conditions, but composite plants used secondary metabolites as scavengers. Data revealed that composite plants managed to produce high amounts of various secondary metabolites in a hydroponic system.