LAUSR

Glycyrrhiza uralensis Fisch. is known as a common Chinese medicinal herb used to harmonize the effects of other ingredients in most Chinese herbal prescriptions. The rapid production of flavonoids in vitro remains unknown in G. uralensis Fisch. To investigate the in vitro adventitious root regeneration and flavonoid accumulation characteristics in G. uralensis for restrictions on collecting wild plants, suspension cultural and freezing microtomy with histochemical assays were carried out. We reported that multiple adventitious roots were initiated from hypocotyls and stems of G. uralensis. Indole-3-butyric acid (IBA) was more conducive than NAA (1-naphthaleneacetic acid) in inducing G. uralensis adventitious roots, but the addition of 6-BA (6-benzylaminopurine) and KT (kinetin) suppressed the formation of adventitious roots. While the concentration of IBA was 1.0 mg L−1, the flavonoid content and yield were the highest at 19.96 mg g−1 and 1.23 mg g−1, respectively. The optimum medium for adventitious root induction was 1/4-strength Murashige and Skoog’s medium containing 0.1 mg L−1 IBA. The content of flavonoids in adventitious roots and apicals cultured in vitro was higher than that in suspension callus, reaching 3.87 times the callus flavonoid content. The histochemical localization of flavonoids showed that G. uralensis flavonoids mainly distributed in the epidermal parenchyma cells of the callus outer layers and gradually accumulated in cell wall and cell gaps of the epidermis and endodermis of adventitious roots along with the primary growth of adventitious roots, indicating that there were no flavonoids in the roots at the early stage of adventitious roots formation. The results showed that calli inducing adventitious roots and apicals for 30 days obtained the highest yield of flavonoid, indicating effective production for flavonoids instead of wild culture. AlCl3 ethanol solution was better than NaOH aqueous solution in terms of chromogenic and localization effects. We concluded that the highest yield of flavonoid and effective production for flavonoid instead of wild culture could be obtained from calli inducing adventitious roots and apicals.