Impact of chronic ozone on soybean growth and biomass partitioning

This study evaluated yield production and changes in the patterns of functional growth analysis parameters of greenhouse-grown soybeans exposed to low concentrations of ozone (O₃). Plants were exposed over a 113-day interval for 341 h to four concentrations of O₃ (2.0, 4.6, 7.0 and 9.7 pphm O₃) on an intermittent basis. Destructive harvests were periodically taken from all treatments to monitor plant response and to provide the basis for growth analysis techniques. Relative to the ambient greenhouse air control treatment (2.0 pphm O₃), 7.0 and 9.7 pphm O₃ typically reduced plant biomass accumulation, leaf area and expansion, relative growth rate, unit leaf rate, seeds per plant (35% reduction), and other yield components; however, the growth and yield parameters of the 4.6 pphm O₃ treatment were often stimulated. With this one exception, O₃ reduced soybean vegetative growth and altered the pattern of biomass partitioning. As a consequence, the soybean yields were also reduced.