Ozone exposure- and flux-based response relationships with photosynthesis of winter wheat under fully open air condition

摘要

AbstractFive winter wheat cultivars were exposed to ambient (A-O3) and elevated (E-O3, 1.5 ambient) O3in a fully open-air fumigation system in China. Ozone exposure- and flux based response relationships were established for seven physiological variables related to photosynthesis. The performance of the fitting of the regressions in terms of R2increased when second order regressions instead of first order ones were used, suggesting that effects of O3were more pronounced towards the last developmental stages of the wheat. The more robust indicators were those related with CO2assimilation, Rubisco activity and RuBP regeneration capacity (Asat,JmaxandVcmax), and chlorophyll content (Chl). Flux-based metrics (PODy, Phytotoxic O3Dose over a threshold ynmolO3m−2s−1) predicted slightly better the responses to O3than exposure metrics (AOTX, Accumulated O3exposure over an hourly Threshold of X ppb) for most of the variables. The best performance was observed for metrics POD1 (Asat,JmaxandVcmax) and POD3(Chl). For this crop, the proposed response functions could be used for O3risk assessment based on physiological effects and also to include the influence of O3on yield or other variables in models with a photosynthetic component.Graphical abstractDisplay OmittedHighlights•5 modern cultivars of wheat were investigated under fully open-air field conditions.•Regressions of photosynthetic responses with different O3metrics were calculated.•Performance was slightly better for flux-based than for exposure-based O3metrics.•The more robust indicators wereAsat,Jmax,Vcmaxand chlorophyll content.