Fig. 1. Reproductive developmental stage (R-stage) for (A) pot-grown and (B) ground-grown Essex soybean treated with combinations of CO₂ and O₃ concentrations in the 1999 experiment. Values are means from three replicate chambers per treatment combination. Ozone treatments were charcoal-filtered (CF) air (24 nmol O₃ mol^–1) and nonfiltered (NF) air plus O₃ (75 nmol O₃ mol^–1). Carbon dioxide treatments were ambient (373 µmol CO₂ mol^–1) and elevated (699 µmol CO₂ mol^–1). Treatments were CF air-ambient CO₂ (CF-373), CF air-elevated CO₂ (CF-699), NF air plus O₃–ambient CO₂ (OZ-373), and NF air plus O₃–elevated CO₂ (OZ-699).