text: Regardless of atmospheric oxygen concentration, shoots of both mint and thyme exposed to elevated CO 2 produced substantially more biomass than shoots grown at 350 ppm CO 2 . At an ambient O 2 concentration of 21%, for example, CO 2 -enriched shoots of mint and thyme attained fresh weights that were 3.1- and 5.8-fold greater, respectively, than those reached by shoots exposed to ambient O 2 and CO 2 concentrations. What it means