Search

Previous studies reveal that atmospheric CO 2 enrichment can improve plant growth with enhanced photosynthesis. However, it is not well-understood whether biochar could be coupled with elevated CO 2 to further promote growth and quality of medicinal plants. This study aims to investigate the interactive effects of CO 2 enrichment and biochar amendment on the growth and quality of a common medicinal plant (Pseudostellaria heterophylla (Miq.) Pax). Two CO 2 concentrations (400 and 1000 ppm) and three biochar dosages (0, 3% and 5%) were considered and tested. Compared with the control in the ambient CO 2 without biochar addition, coupled CO 2 enrichment and 3% biochar enhanced available nutrient levels (e.g., P) most efficiently by up to 1740% in rhizosphere. This was due to the increased soil enzyme activity and relative abundance of beneficial bacteria for nutrient activation. Elevated CO 2 (1000 ppm) coupled with 3% biochar induced the highest tuber yield of P. heterophylla , which was 228% higher than the control. Coupled elevated CO 2 and 5% biochar group shows an increasing yield by 84%. The coupled treatments could increase the yield by up to 213% as compared with the only biochar or only elevated CO 2 treated groups. The concentrations of polysaccharides in root tuber were improved by 56–124% under the CO 2 enrichment. They all satisfy the requirements of Hong Kong Chinese Materia Medica Standards. However, the concentrations of saponins decreased by 14–20% in low dosages of biochar treated groups (0, 3%) under the elevated CO 2 concentration, as compared with those under the ambient CO 2. On the contrary, CO 2 enrichment increased the concentrations of saponins by 22% when biochar dosage increased to 5%. This study recommends that 3% biochar amendment coupled with 1000 ppm CO 2 should be adopted to enhance the yield and biosynthesis of polysaccharides in root tuber of P. heterophylla. [Display omitted] • Available P in rhizosphere dramatically increased under coupled CO 2 and biochar. • Enzymes-producing bacteria were enhanced under elevated CO 2 with 3% biochar. • Interactive effects of CO 2 and biochar on plant growth and yield were synergistic. • CO 2 enrichment improved the concentration of polysaccharides in medicinal organ. • Elevated CO 2 alleviated the adverse effects of high biochar dose on saponin synthesis. [ABSTRACT FROM AUTHOR]