Effect of continuous lighting on the growth and leaf chemical components of Artemisia princeps grown hydroponically in a plant factory condition

Young leaves of Artemisia princeps Pamp. (Japanese mugwort), already used as a foodstuff in Japan, can be positioned as a functional health food because of remarkably higher contents of chlorogenic acid and total polyphenol compared to common vegetables. To procure young leaves in demand on a year-round basis by hydroponic production in fully artificial light-type plant factories, we investigated whether 24-h photoperiod, known to enhance some beneficial constituents, could improve the growth and chemical constituents of Japanese mugwort plants grown hydroponically in a plant factory condition. As we previously demonstrated that lowering the nutrient solution concentration increased chlorogenic acid and total polyphenol contents of the leaves without reducing the growth, plants were cultivated with a lower concentration of nutrient solution. The results indicated that it is possible to grow Japanese mugwort hydroponically under 24-h photoperiod in a plant factory condition with a nutrient solution concentration as low as 25% of the standard. In addition, under 24-h photoperiod, plant growth was greatly accelerated and chlorogenic acid as well as total polyphenol were increased, suggesting that 24-h photoperiod is highly beneficial for Japanese mugwort production in a fully artificial light-type plant factory.