Effectiveness of silver nitrate application on plant growth and bioactive compounds in Agastache rugosa (Fisch. & C.A.Mey.) kuntze

The objective of this study was to determine the optimal dose of silver nitrate (AgNO(3)) for plant growth and to increase the main bioactive compounds in A. rugosa cultivated in a hydroponic system. The application of soaked diniconazole (120 μmol mol(−1)) to all plants at 7 days after transplanting (DAT) for dwarfing plant height, optimizing cultivation space in the plant factory. Subsequently, plants were soaked with 50, 100, 200, and 400 μmol mol(−1) AgNO(3) for 10 min at 25 DAT and harvested at 39 DAT. The results indicated that 200 and 400 μmol mol(−1) treatments tended to severely decrease plant growth parameters compared to treatments with lower concentrations. The net photosynthetic rate was significantly reduced by the 200 and 400 μmol mol(−1) treatments compared to treatments with other concentrations. The 400 μmol mol(−1) treatment led to the lowest concentrations of chlorophyll a, chlorophyll a/b, total carotenoid, chlorophyll b, and the total chlorophyll. However, 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity was considerably increased in 50, 100, 200, and 400 μmol mol(−1) compared to that of the control plants. A higher rosmarinic acid (RA) concentration in the whole plant was noticed with the 400 μmol mol(−1) treatment compared with that of the untreated plants. The 100 μmol mol(−1) treatment exhibited the highest concentration and content of tilianin in the whole plant. Concentration of acacetin 1 significantly increased in the whole plant with 100 and 200 μmol mol(−1) treatments compared with that of the untreated plants. Concentrations of acacetin 2 and 3 in the whole plant were the highest with 100 and 200 μmol mol(−1) treatments, respectively. The results demonstrated that 100 μmol mol(−1) treatments can be used to increase bioactive compounds without severely limiting the plant growth and reducing chlorophyll concentrations of A. rugosa. Implementing this optimal dose can enable growers and researchers to cultivate A. rugosa more efficiently, enhancing bioactive compound content and overall plant performance, thus harnessing the potential health benefits of this valuable plant species.