Comparison of Atmospheric O 3 Dose–Response Effects Under N Addition on Gas Exchange, Growth, and Biomass of Raphanus sativus L.

Regional increases in atmospheric O3 are phytotoxic not only to major crops but also to root vegetables such as radish, and their effects can be further modulated by nitrogen (N) addition. To assess how cherry radish responds to elevated O3 (eO3) under N addition and to compare the dose–response relationships, we established six open-top chambers with two O3 levels and two N treatments in Beijing, China, to examine gas exchange, growth, and biomass throughout the growing period. The results showed that: 1. eO3 had a “priming effect” on photosynthesis rates (Pn) at the beginning of the experiment. N addition alleviated the O3-induced Pn reduction at the end of the experiment by 6.76% but did not significantly influence the O3-dose response to Pn; 2. stomatal conductance (gs) did not have a dose response to all treatments while evaporation rates (E) showed strong negative regression with AOT40; 3. N addition reduced the hypocotyl biomass (−47.70%), leaf biomass (−32.22%), and the whole plant biomass reduction caused by O3 (−38.47%) at the end of the experiment, but N addition did not significantly influence O3-dose response to biomass. In conclusion, N addition can alleviate O3-induced reductions in Pn and biomass via non-stomatal mechanisms, but it is ineffective in altering long-term O3 dose–response relationships. Soil N addition offers a short-term strategy to mitigate O3 impacts on short-lived root vegetables such as cherry radish but does not influence key functional traits over the long term. This study highlights the potential of N addition to alleviate acute oxidative stress, while underscoring its limitations in mitigating the effects of prolonged O3 exposure in root vegetables.

Abstract licence: CC BY

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