Fig. 2. The percentage stimulation of seed yield for nine soybean cultivars grown at elevated CO₂ (71 Pa, E) relative to the ambient CO₂ treatment (40 Pa, A) over three runs of the experiment. Cultivars are listed according to the relative response of seed yield to elevated CO₂. * indicates a significant difference (P < 0.05) relative to ambient CO₂ for individual cultivars. Bars are ±se