Visible symptoms and changes in physiological parameters of <i>Cinnamomum camphora</i> and <i>Michelia chapensis</i> under ozone stress

The responses of Cinnamomum camphora and Michelia chapensis to ozone (O3) exposure in terms of the O3 injury and changes in the physiological parameters of their leaves were examined in charcoal-filtered (CF) air and O3 at 1×, 2×, and 4×O3 ambient concentrations in open-top chambers in an eight-month experimental period. High levels of O3 exposure led to visible injuries in both species. The increased chlorophyll content in the second month and increased carotenoid content of the 1×O3 treatment group at the end of experiment were identified as hormetic-compensatory strategies that enhance tolerance and acclimation to O3 stress. Significant interaction effect between O3and tree species with respect to the superoxide dismutase (SOD) activity and proline content suggests that the effects induced by O3 were highly dependent on the tree species. C. camphora showed more foliar injury symptoms and greater O3-induced decreases in the chlorophyll, carotenoid, and protein contents than M. chapensis, which suggests that C. camphora is more sensitive to O3 than M. chapensis.