Tropospheric ozone rapidly decreases root growth by altering carbon metabolism and detoxification capability in...

High tropospheric ozone (O₃) concentrations lead to significant global soybean (Glycine max) yield reductions. Research concerning O₃ impacts on soybean has focused on the contributions of above-ground tissues. In this study, Mandarin (Ottawa) (O₃-sensitive) and Fiskeby III (O₃-tolerant) soybean genotypes provide contrasting materials to investigate O₃ effects on root growth. We compared root morphological and proteomic changes when 16-day-old plants were treated with charcoal-filtered (CF) air or elevated O₃ (80 ppb O₃ for 7 h/day) in continuously stirred-tank reactors (CSTR) for 7 days. Our results showed that in Mandarin (Ottawa), decreased expression of enzymes involved in the tricarboxylic acid (TCA) cycle contributes to reduction of root biomass and diameter under elevated O₃. In contrast, O₃ tolerance in Fiskeby III roots was associated with O₃-dependent induction of enzymes involved in glycolysis and O₃-independent expression of enzymes involved in the ascorbate-glutathione cycle. We conclude that a decreased abundance of key redox enzymes in roots due to limited carbon availability rapidly alters root growth under O₃ stress. However, maintaining a high abundance of enzymes associated with redox status and detoxification capability contributes to overall O₃ tolerance in roots.