Substantial yield reduction in sweet potato due to tropospheric ozone, the dose-response function

Impacts of tropospheric ozone on sweet potato (Ipomoea batatas) are poorly understood despite being a staple food grown in locations deemed at risk from ozone pollution. Three varieties of sweet potato were exposed to ozone treatments (peaks of: 30 (Low), 80 (Medium), and 110 (High) ppb) using heated solardomes. Weekly measurements of stomatal conductance (gs) and chlorophyll content (CI) were used to determine physiological responses, along with final yield. gs and CI were reduced with increasing ozone exposure, but effects were partially masked due to elevated leaf senescence and turnover. Yield for the Erato orange and Murasaki varieties was reduced by similar to 40% and similar to 50% (Medium and High ozone treatments, respectively, vs Low) whereas Beau -regard yield was reduced by 58% in both. The DO3SE (Deposition of Ozone for Stomatal Exchange) model was parameterized for gs in response to light, temperature, vapour pressure deficit and soil water potential. Clear responses of gs to the environmental parameters were found. Yield reductions were correlated with both concentration based AOT40 (accumulated ozone above a threshold of 40 ppb) and flux based POD6 (accumulated stomatal flux of ozone above a threshold of 6 nmol m(-2) s(-1)) metrics (R-2 0.66 p = 0.01; and R-2 0.44 p = 0.05, respectively). A critical level estimate of a POD6 of 3 (mmol m(-2) Projected Leaf Area(-1)) was obtained using the relationship. This study showed that sweet potato yield was reduced by ozone pollution, and that stomatal conductance and chlorophyll content were also affected. Results from this study can improve model predictions of ozone impacts on sweet potato together with associated ozone risk assessments for tropical countries.

Automated summary

This study investigated the effects of tropospheric ozone on sweet potato and found that ozone exposure reduced yield, stomatal conductance, and chlorophyll content. The results can improve model predictions of ozone impacts on sweet potato and contribute to ozone risk assessments in tropical countries.