Liquorice (Glycyrrhiza glabra L.) has been used worldwide as a medicine for a long time. In this research, the effect of silver nitrate (AgNO 3 ) as a growth regulator and anti-ethylene in in vitro culture was investigated on growth and anatomical structure of vegetative organs (root, hypocotyl, shoot, leaf) as well as the number of stomata and trichomes in the leaves of liquorice under vitro culture condition. The seeds were cultured in MS culture media containing different concentrations of AgNO 3 (0, 2, 4, 8, and 10 mg L -1 ). Investigations on 20-day seedlings after three replications showed a significant increase in length and growth of roots, hypocotyls and shoots, and decreased number of stomata and trichomes in the samples treated with AgNO 3 (P≤0.05). The effects of AgNO 3 on anatomical structures of the organs included the increased cell division in root and shoot tips, reduced vascular tissues and sclerenchyma-fiber (with lignified cell walls), increased thickness of Casparian strip and cell walls of endodermis, reduced thickness of epidermis and increased intercellular spaces in mesophyll. The leaf area was measured in the 4-month plantlets, showing a significant increase in the samples treated with AgNO 3 . Furthermore, there was significant difference in increased leaf area applying 10 mg L -1 treatment and other concentrations as well as between the concentrations of 2 and 8 mg L -1 . It seems that these results are due to the inhibitory effects of AgNO 3 on the production and function of ethylene and the plant strategy to increase the tolerance against silver metal.

Liquorice (Glycyrrhiza glabra L.) is a plant that has been considered for a long time due to its valuable secondary metabolites. This study was conducted to obtain quercetin and glycyrrhizin under controlled conditions and the use of silver nitrate (AgNO3) as an elicitor to increase their production. For this purpose, the seeds were cultured in MS media containing various concentrations of AgNO3 (0, 2, 4, 8 and 10 mg L-1). Quercetin in the aerial parts extract of three-month seedlings prepared with methanol solvent 95% and acetic acid (9:1), and glycyrrhizin in the root extract of four-month seedlings prepared with ethanolic extract (30%) were evaluated qualitatively and quantitatively using HPLC. The results obtained from three replications showed the presence of quercetin and glycyrrhizin in all samples. The amount of quercetin in all samples treated with AgNO3 was significantly higher than control (P≤0.05) and this increase was higher at concentrations of 8 and 10 mg L-1 in comparison with other concentrations. Glycyrrhizin content increased under the influence of different concentrations of AgNO3 as compared to the control; however, this increase was not significant. Our results clearly showed that this method is a practical method to produce and elicit more these compounds with medicinal value.