Effects of elevated concentrations of CO2 and O3 singly or in mixture on the growth of several herbaceous wild plant species

Abstract

Effects of elevated concentrations of CO2 and/or O3 on the growth of Amaranthus mangostanus L., Bidens frondosa L., Galinsoga ciliata Blake and Portulaca oleracea L. were investigated using environment-controlled growth cabinets. Dry weight and leaf area increased with an increase in CO2 concentration (400-2000ppm). In B. frondosa and G. ciliata, high CO2 increased RGR due to an increase in NAR, while it decreased LAR due to a decrease in SLA. In A. mangostanus and P. oleracea, these parameters were hardly changed by CO2 concentrations. Transpiration was reduced with an increase in CO2 concentration, especially P. oleracea. Elevated concentrations of O3 decreased RGR due to a decrease in NAR in G. ciliata and due to decreases in NAR and LAR (SLA) in P. oleracea, a O3-sensitive species. In G. ciliata, 0.05ppm O3 accelerated transpiration, while higher concentrations of O3 reduced it in G. ciliata and P. oleracea. These changes should be due to the changes in leaf conductance which seemed similar to those in NAR. In the present study, CO2 and O3 effects were independent. The “global warming” might change the species composition and ecosystems in the future.