Mycorrhiza and Silicon Influence Glycyrrhiza glabra L. under Water-deficit; Antioxidant Activity, Medicinal Metabolites and Mineralogical Analysis

Background: Exogenous application of silicon (Si) and arbuscular mycorrhizal fungi (AMF) can help plants cope with drought stress. An experiment was designed with two Si solute levels in irrigation water (i.e. 0 (Si 0 ) and 300 mg/L (Si 1 )), two levels of AMF inoculation (i.e. inoculation with Claroiedoglomus etunicatum (F 1 ) and without inoculation (F 0 )), and five soil moisture regimes (i.e. 100, 80, 60, 40 and 20% of field capacity (FC). After two months, the licorice roots were harvested and analyzed.ResultsUnder water deficit conditions, there were significant decreases in root length and dry weight (DW) ( p  < 0.05), compared to the control. Si and AMF could significantly ( p  < 0.05) enhanced root area (47.75-150.64 cm 2 ) under all irrigation levels. The maximum glycyrrhizic acid (26.62 mg/g DW ) was achieved by the interaction between Si and AMF in response to 40% FC. A reduction in total flavonoids and phenolics of licorice was observed under severe drought levels; however, the Si and AMF acted to increase sinapic acid (16.46 mg/g DW ), and trans ferulic acid (1.11 mg/g DW ) in roots. The results indicated that the interaction between Si and AMF positively affected nitrogen and phosphorous concentrations in roots (53.51 and 74.07%, respectively). Also, there was an increase in potassium concentration in response to 100, 80, and 40% FC among Si-treated plants (38.5–44.7%).ConclusionIn conclusion, the exogenous application of Si and AMF showed a synergistic impact on the ability to mitigate the adverse effects of drought stress by improving plant growth and enhancing metabolite accumulation in licorice.