Fig. 2. Relative seed yields combined for both years of the experiment (1999 and 2000) for Essex soybean grown in large pots or in the ground. Plants were treated with combinations of CO₂ and O₃ concentrations throughout the two growing seasons. Ozone treatments were charcoal-filtered (CF) air (22 to 24 nmol O₃ mol^–1) and nonfiltered (NF) air plus O₃ (67 to 75 nmol O₃ mol^–1). Carbon dioxide treatments were ambient (369 to 373 µmol CO₂ mol^–1) and elevated (699 to 717 µmol CO₂ mol^–1). Treatments were CF air-ambient CO₂ (CF-A), CF air-elevated CO₂ (CF-CO2), NF air plus O₃–ambient CO₂ (OZ-A), and NF air plus O₃–elevated CO₂ (OZ-CO2). Relative treatment effects on seed yield for pot-grown and ground-grown plants are shown as a percentage of their respective control treatment (CF-A). Values are means ± SE.