Elevated CO2 increases biomass and tuber yield in potato even at high ozone concentrations

Changes in the growth and yield of field-grown potato (Solanum tuberosum cv . Bintje) induced by season-long elevated CO2 and/or ozone concentrations a re reported. Open-top chambers and unchambered field plots were used to examine crop res ponses to three CO2 (ambient, 550 and 680 mu mol mol(-1)) and two ozone (am bient and 65 nmol mol(-1), 8 h d(-1) seasonal mean) treatments applied thro ughout the 105 d growing season. Elevated CO2 increased both above- and below-ground biomass at intermediate and final harvests. Tuber yield at final harvest was increased by c. 40% d ue to an increase in mean tuber weight rather than tuber number; tuber yiel d did not differ significantly between the 550 and 680 mu mol mol(-1) CO2 t reatments. Elevated ozone had no significant effect on growth or yield exce pt for the largest size category of tubers, despite extensive visible folia r injury. Significant CO2 x ozone interactions were detected only for senes cent leaf number and green leaf ratio. Elevated CO2 increases biomass and tuber yield in S. tuberosum cv. Bintje e ven at high ozone concentrations; these findings are discussed in relation to predicted future atmospheric changes.