Physiologic and Metabolic Changes in According to Different Energy Levels of UV-B Radiation.

Ultraviolet B (UV-B) light, as a physical elicitor, can promote the secondary metabolites biosynthesis in plants. We investigated effects of different energy levels of UV-B radiation on growth and bioactive compounds of . Three-week-old seedlings were grown in a plant factory for 5 weeks. Plants were subjected to different levels of UV-B (0, 0.1, 0.25, 0.5, 1.0, and 1.25 W m), 6 h a day for 6 days. All UV-B treatments had no negative effect on the shoot dry weight; however, relatively high energy treatments (1.0 and 1.25 W m) inhibited the shoot fresh weight. UV-B light of 0.1, 0.25, and 0.5 W m did not affect total chlorophyll and HO contents; however, they increased total carotenoid content. On 4 days, 0.25 W m treatment increased antioxidant capacity, total hydroxycinnamic acids (HCAs) content, and several sesquiterpenes. Treatments with 1.0 and 1.25 W m increased total carotenoid, total HCAs, and HO contents, and destroyed chlorophyll pigments, reducing maximum quantum yield of photosystem II and causing visible damage to leaves. Partial least squares discrimination analysis (PLS-DA) showed that secondary metabolites were distinguishably changed according to energy levels of UV-B. The potential of 0.25 W m UV-B for the efficient production of bioactive compounds without growth inhibition in was identified.