Interactive Effects of Ultraviolet Irradiation and Biochar Treatment on the Growth and Active Ingredients of Pseudostellaria heterophylla.

UVA and UVB are two main components of solar ultraviolet (UV) radiation. Some studies have reported the impacts of UV irradiation on plant secondary metabolism and plant growth. However, the role of UV irradiation in plant growth and quality in biochar-treated soils is poorly understood. This study aims to investigate the interactive effects of UV irradiation and biochar application on the growth and quality of Pseudostellaria heterophylla (Miq.) Pax, a popular medicinal plant. Three UV irradiation conditions (no UV irradiation, UVA irradiation at 2.5 W/m² for 12 h/day and UVB irradiation at 0.05 W/m² for 0.5 h/day) were considered in biochar-free and biochar (3%)-amended soils. The non-UV irradiated biochar-treated group exhibited the highest tuber yield. UVA irradiation reduced the yield improvement efficiency of biochar, while under UVB irradiation, biochar treatment reduced the tuber biomass. This were mainly because the application of high-nutrient biochar increased plant sensitivity to UV radiation. The UVA-irradiated group without biochar treatment exhibited the maximum polysaccharide concentration in the tuber, which was 38% higher than that of the control. Biochar application inhibited polysaccharide synthesis under UV treatment. The saponin concentration in the tuber was enhanced by up to 79% under UV (particularly UVB) irradiation. The coupled UVB and biochar treatment significantly enhanced saponin synthesis. These results indicate the interactive effects of UV irradiation and biochar treatment on P. heterophylla. Therefore, biochar amendment without UV irradiation is suggested to improve the tuber yield of P. heterophylla. UVA (2.5 W/m² for 12 h/day) treatment is recommended for higher active ingredient concentration. However, the negative effects of UV irradiation on biochar-induced plant growth promotion should be also considered. This research provides a basis for practical large-scale cultivation in the future. [ABSTRACT FROM AUTHOR]