High Electrical Conductivity of Nutrient Solution and Application of Methyl Jasmonate Promote Phenylpropanoid Production in Hydroponically Grown Agastache rugosa

Abstract

Agastache rugosa Kuntze, a perennial herb in the Labiatae family, is ubiquitous in Korean fields and is used as a wild vegetable and medicinal herb for traditional therapies. We measured the concentrations of tilianin and acacetin, in hydroponically grown A. rugosa plants cultured in nutrient solutions of various electrical conductivities (ECs) for four weeks and sprayed or not with different concentrations of methyl jasmonate (MeJA). The total acacetin content of A. rugosa shoots ranged from 41.17 mg/plant at 1.0 dS.m(-1) to 50.00 mg/plant at 4.0 dS.m(-1) , but did not differ significantly between treatments. Tilianin accumulation in A. rugosa at 2.0 and 4.0 dS.m(-1) was 9.66 and 8.64 mg/plant, respectively, values significantly greater than those observed at 1.0 dS.m(-1). The combined effect of MeJA application and the EC of the nutrient solution influenced the production of both tilianin and acacetin in appreciable amounts. The highest observed levels of tilianin were 2.75 mg.g(-1) at 4.0 dS.m(-1) , 2.49 mg.g(-1 )at 2.0 dS.m(-1) , and 1.62 mg.g(-1)at 1.0 dS.m(-1) after application of 20 JIM MeJA. Similarly, the highest observed levels of acacetin were 33.81 mg.g(-1) at 4.0 dS.m(-1) and 20.85 mg.g(-1 )at 2.0 dS.m(-1) after application of 10 mu M MeJA. We also evaluated the growth parameters of these plants. All growth parameters were affected by the EC of the nutrient solution. The greatest leaf length and width and the longest petiole, internode, and stem measurements were observed at 2.0 dS.m(-1) , but these values were lower at 4.0 dS.m(-1). All root parameters increased with increasing EC, peaking at 4.0 dS.m(-1). Our results suggest that high EC nutrient solution together with MeJA application provides optimum conditions for plant growth and accumulation of tilianin and acacetin in hydroponically grown A. rugosa.