Biomass response of Schinus terebinthifolia to elevated ozone: evidence for a dose-dependent hormetic effect

Abstract Schinus terebinthifolia (Raddi) is a tropical fast-growing broadleaf tree species in Brazil’s Atlantic Forest, a threatened biodiversity hotspot. The species has socioeconomic importance, is used in forest restoration programs and urban greening. In urban environments, plants are exposed to several abiotic stressors such as atmospheric pollution. Tropospheric ozone (O 3 ) is one of the main secondary pollutants that affect plant growth and survival. Therefore, determining the critical levels (CL) of phytotoxic O 3 is essential. Ozone risk assessment for S. terebinthifolia is unknown. Forty-five S. terebinthifolia seedlings were cultivated in pots and submitted to five ozone treatments for three months in an O 3 -free-air controlled facility. Ozone risk assessment was based on environmental data, measurements of stomatal O 3 uptake and seedling biomass. To find the best model for predicting O 3 -induced biomass loss, we tested the accumulated ozone exposure over a threshold of 40 ppb (AOT40) and the phytotoxic ozone dose above a threshold ‘y’ (POD y ) using linear and 116 nonlinear statistical models. POD 16 and POD 15 when applied with the four-parameter nonlinear logarithmic model “Bragg4” provided the best fit for assessing O 3 risk based on total biomass and leaf biomass, respectively. The species had a 4% biomass loss at 2.56 mmol O 3 m −2 POD 16 and in leaf biomass at 3.37 mmol O 3 m −2 POD 15 . The results indicate that biomass accumulation was stimulated at low to moderate O 3 levels but reduced at higher levels. Overall, S. terebinthifolia demonstrated a high tolerance to tropospheric O 3. Graphical abstract