Pseudostellaria heterophylla, a herbaceous perennial plant of the Caryophyllaceae family, is one of the most popular traditional Chinese medicinal plants. Its medicinal organ (i.e., root tuber) contains various compounds (e.g., polysaccharides, saponins) with high medicinal value. However, the biomass and quality of its medicinal organ decline significantly because of soil sickness (e.g., nutrient deficiency, pathogen accumulation) after replanting. Soil amendments are commonly used to promote soil properties and consequent plant growth. Additionally, climatic variables (i.e., atmospheric CO2, UV radiation) play vital roles in plant growth and quality. However, effects of atmospheric CO2 and UV radiation combined with soil amendment (i.e., biochar) on medicinal plants are not well-unde...[ Read more ]

Pseudostellaria heterophylla, a herbaceous perennial plant of the Caryophyllaceae family, is one of the most popular traditional Chinese medicinal plants. Its medicinal organ (i.e., root tuber) contains various compounds (e.g., polysaccharides, saponins) with high medicinal value. However, the biomass and quality of its medicinal organ decline significantly because of soil sickness (e.g., nutrient deficiency, pathogen accumulation) after replanting. Soil amendments are commonly used to promote soil properties and consequent plant growth. Additionally, climatic variables (i.e., atmospheric CO2, UV radiation) play vital roles in plant growth and quality. However, effects of atmospheric CO2 and UV radiation combined with soil amendment (i.e., biochar) on medicinal plants are not well-understood. This study aims to investigate atmospheric CO2 enrichment and UV radiation effects on growth and quality of P. heterophylla in biochar amended soils.

Firstly, GGBS as a representative inorganic soil amendment was used to treat plants against heavy metal toxicity. Three levels (0, 3%, 5% by mass) of GGBS application were considered. Apart from inorganic amendment, biochar, a sustainable soil amendment with abundant organic matter, was modified and applied for comparison. P-modified and unmodified biochar (peanut shell) at dosages of 0, 3% and 5% (by mass) were considered. Thereafter, coupled effects of elevated CO2 and biochar on plants were studied. Three dosages (0, 3% and 5%, by mass) of biochar and two levels (400, 1000 ppm) of atmospheric CO2 were applied. Finally, interactive effects of biochar and UV (i.e., UVA, UVB) radiation on the growth and quality of P. heterophylla were investigated. Biomass of root tuber was the indicator of P. heterophylla yield. Active ingredient concentration was the primary parameter to evaluate the quality of medicinal plants.

GGBS reduced Cd and Cu accumulation in plant organs by 69-86% and 10-30% respectively and increased plant yield by 10-46%. However, the concentrations of active ingredients in P. heterophylla tuber decreased by up to 36% due to GGBS treatment. P-modified biochar improved the tuber yield significantly by 69-136%. The concentrations of active ingredients in tubers were increased by 3-79% under P-modified biochar. As the application of P-modified biochar increasing from 0 to 5%, the yield and quality of P. heterophylla were consequently promoted. Elevated CO2 significantly promoted the tuber yield by 125-259% under 3-5% biochar supply. Increased promotion efficiency of CO2 enrichment on plant yield was presented at higher biochar dosage with significant interactive effects. The concentration of polysaccharides in root tuber was significantly improved by 56-124% under CO2 enrichment. However, biosynthesis of saponins was slightly inhibited by elevated CO2. In contrast to improved yield in non-UV condition, biochar showed reduced enhancement under UVA radiation and even inhibited the tuber biomass in UVB condition. However, UVA irradiated plants had highest yield among the groups without biochar. Polysaccharide synthesis in tuber was enhanced by 12-38% under UVA but reduced by 29-41% under UVB exposure. Compared with control, UVA irradiated plant without biochar showed significant increase of polysaccharides concentration. Saponins in tuber were stimulated by radiation of UV, especially UVB (increase by 20-79%). Coupled treatments of biochar and UVB led to the significant improvements on saponins synthesis.