OZONE, CO2 ASSIMILATION AND PSII FUNCTION IN URBAN TREES: THE CASE OF TILIA AMERICANA
Air pollution is one of the main environmental problems in urban areas and not only. In particular, ozone concentration in urban atmosphere during the warm season may be, for many hours, well above 100 ppb. Plant responses to ozone vary significantly among species: the genus Tilia, for instance, generally does not show any foliar injury induced by this pollutant under natural conditions. Measurements of leaf gas exchange under saturating light and chlorophyll a fluorescence parameters were performed on T. americana during 45 consecutive days of exposure (120 ppb of ozone, 5 h d-1). Although at the end of the fumigation the plants did not exhibit any visible foliar symptoms, ecophysiological parameters were altered starting from 15 days after the beginning of treatment. Ozonated plants compared to controls showed stomatal closure (-15%) and a significant decrease of photosynthetic activity (-61%). Fluorescence parameters analysis (at the end of the treatment) suggested that the light reactions were virtually altered in treated plants as demonstrated by a change in photochemical quenching (-17%) and in quantum yield of non-cyclic electron flow (-34%), indicating an effect of ozone on the PSII reaction centre. At the end of exposure, malondialdehyde content (an indicator of lipid peroxidation) increased in the treated-plants (+18%, compared to controls).
Pellegrini, E., Francini, A., Lorenzini, G. and Nali, C. (2010). OZONE, CO2 ASSIMILATION AND PSII FUNCTION IN URBAN TREES: THE CASE OF TILIA AMERICANA. Acta Hortic. 881, 539-542
air pollution, oxidative stress, ornamental species, photosynthesis, chlorophyll fluorescence, quenching analysis