Ozone dose-response relationships for wheat can be derived using photosynthetic-based stomatal conductance models

Ground-level ozone (O3) pollution occurs across many important agricultural regions in Europe, North America, and Asia, negatively impacting O3-sensitive crops such as wheat. Risk assessment methods to quantify the magnitude and spatial extent of O3 pollution have often used dose-response relationships. In Europe, the dose metrics used in these relationships have evolved from concentration- to flux-based metrics since stomatal O3 flux has been found to correlate better with yield losses. Estimates of stomatal conductance (gsto) have to date used an empirical multiplicative model. However, other more mechanistic approaches are available, namely the coupled photosynthetic-stomatal conductance (Anetgsto) model. This study used a European O3 OTC and solardome fumigation experimental dataset (comprising 6 cultivars, 4 countries and 14 years) to develop a new flux-based dose-response relationship for wheat yield using the mechanistic Anetgsto model (Anetgstomech). The Anetgstomech model marginally improved the regression of the dose-response relationship (R2 = 0.74) when compared to the flux-response models derived from empirical gsto models. In addition, the Anetgstomech model was somewhat better at predicting the effect of high O3 concentrations on diurnal and seasonal profiles of gsto and Anet. It was also better able to simulate changes of up to 7 and 12 days, respectively, in the start (SOS) and end (EOS) of senescence, an important determinant of yield loss, over a range of O3 treatments. We conclude that Anetgstomech model can be used to derive robust flux-response relationships.