Analysing the impact of ozone on biochemical and physiological variables in plant species belonging to natural ecosystems

Physiological and biochemical responses to acute ozone exposure for 29 plants belonging to natural and semi-natural european ecosystems were characterised and used to reveal common features among species. Plants were grown in controlled conditions and exposed to acute ozone fumigation at 150 ppb for 3 h. Parameters of chlorophyll a fluorescence, pigments content and antioxidant enzyme activity were measured in control and ozone-treated plants and the data obtained from these analyses was used to perform multivariate statistics. The results indicated that the treatment with ozone and the species diversity, as well as the interaction between the two factors, were able to significantly affect the variables as a whole. Ozone treatment affected plant metabolism to different extents for the different species, even if the statistical analyses performed proved that most of them could be grouped in two main clusters. The first cluster is mainly affected in the photosynthetic performance, as indicated by the decrease in the Fv/Fm ratio and the increase in the de-epoxidation index, while the second one grouped species characterised by strong reductions in leaf pigment content and by increases in peroxidase activity. The observation that most of the parameters analysed were differently affected by the treatment in the natural and semi-natural species investigated pointed out that the different constitutive metabolic behaviour could account for a different susceptibility to the pollutant and, as a consequence, for a different performance of some of the species in heavily polluted environments.