Effects of seasonal light variation and artificial light treatments on growth and flavonoid production of Artemisia princeps cultivated in greenhouses

Artemisia princeps (Ganghwa wormwood) is a medicinal plant that produces two major flavonoids, eupatilin and jaceosidin, which are used in the treatment of gastritis and peptic ulcers. A. princeps is primarily field cultivated, which has some drawbacks, including only one cultivation period per year and variations in flavonoid production due to environmental changes. The objective of this study was to analyze the effects of seasonal light variation and artificial light treatments on the growth and flavonoid production of A. princeps grown in greenhouses for year-round production. The plants were cultivated and harvested nine times in one year under natural seasonal light conditions in greenhouses. During the winter growth period (when natural light is substantially lower), four artificial light treatments were applied during two cultivation periods, from September 2016 to January 2017: supplemental light, night interruption, low light, and low light with night interruption. The plants grown under the natural light condition in greenhouses were used as a control. After harvest, the growth of the plants was measured, and the contents of eupatilin and jaceosidin were determined. The plants had the highest biomass when the accumulated radiation and duration were highest. The growth and flavonoid production were significantly associated with accumulated radiation and light duration. The supplemental light and night interruption treatments resulted in significantly higher biomass and flavonoid production, with the night interruption treatment requiring less energy input than the supplemental light treatment. Therefore, for consistent biomass and flavonoid production of A. princeps, a night interruption treatment is suggested in greenhouse cultivation during low irradiation and short days (less than 13 h).