Abstract: With medicinal plant Erigeron breviscapus as test material, its biomass and the contents and yields of scutellarin and caffeate were monitored under doubled (800±100) μmol·mol-1 and natural (400±25) μmol·mol-1 CO2 concentration. Comparing with those under natural CO2 concentration, the biomass of E. breviscapus under doubled CO2 concentration increased by 22%, the contents of scutellarin and caffeate increased by 23% and 26%, and the yields of these two constituents increased by 376% and 453%, respectively. Different organs had different responses in their biomass and active constituent contents to the elevated CO2 concentration. Under doubled CO2 concentration, the plant N content decreased by 472% and was negatively correlated with active constituent contents, being accorded well to the C/N balance hypothesis, and the biomass was positively correlated with the active constituent contents while no trade-off was observed between plant growth and secondary metabolism, suggesting that rational application of CO2 could improve the yield and quality of E. breviscapus.

Key words: elevated CO₂, Erigeron breviscapus, growth, flavonoid, caffeate