Effects of UV-B and Far-Red Light Irradiation on the Growth and Active Component Accumulation in Scutellaria baicalensis Seedlings

To investigate the regulatory role of light quality in the medicinal quality formation of Scutellaria baicalensis (S. baicalensis), seedlings of S. baicalensis were subjected to four light treatments: control, ultraviolet-B (UV-B), far-red light (FR), and a combination of UV-B and FR (UV-B+FR). Growth indices, photosynthetic parameters, antioxidant activity, and flavonoid content in the roots were measured after 10 and 30 days of treatment. The results showed that after 30 days of treatment, UV-B irradiation significantly inhibited the biomass accumulation in both leaves and roots but promoted the synthesis of secondary metabolites, with total flavonoid content increased by 6.57% compared with the control. FR treatment promoted both biomass and total flavonoid accumulation, increasing root dry weight by 40.90% and raising total flavonoid content by 3.93% relative to the control. The combined UV-B+FR treatment exhibited a synergistic effect: on one hand, it alleviated UV-B-induced stress damage, increasing root dry weight by 45.13% compared with UV-B alone; on the other hand, it significantly enhanced the synthesis of flavonoids, with baicalin and wogonoside contents increased by 4.30% and 13.85%, respectively, relative to the control. At 10 days of treatment, UV-B and FR significantly affected antioxidant enzyme activities and chlorophyll fluorescence parameters; after 30 days, S. baicalensis showed adaptive recovery with increased chlorophyll content. In conclusion, the combined UV-B and FR treatment regulates the growth and development of S. baicalensis seedlings and promotes the accumulation of medicinal components. These findings provide a theoretical basis for manipulating the light environment in the artificial cultivation of medicinal plants.