Physiological and biochemical changes in tree seedlings growing in urban forest soil contaminated with copper in São Paulo, Brazil

Soil pollution by heavy metals is a worldwide environmental concern. Owing to their proximity to sources of anthropogenic emission, urban forest fragments are highly affected by the excessive input of heavy metals into the soil. Thus, this study aimed to assess the physiological and biochemical responses of two native Brazilian Atlantic Forest tree species, Schinus terebinthifolia Raddi (pioneer species) and Eugenia uniflora L. (non-pioneer species), when cultivated in soils contaminated with Cu. Plants were cultivated in soils of an urban forest fragment contaminated with 0 (control), 60, 120, 180 or 240 mg Cu kg−1 soil. Growth variables, Cu content in plant tissues, translocation index, bioaccumulation factor, pigment contents, leaf gas exchange and chlorophyll fluorescence were all measured to assess physiological alterations resulting from Cu stress, while enzymatic (superoxide dismutase) and nonenzymatic (ascorbic acid and glutathione) antioxidants were quantified to assess the biochemical responses of the species. Both species presented high uptake and accumulation of Cu in roots with low translocation rates to shoots; however, S. terebinthifolia showed higher Cu restriction in roots than E. uniflora. S. terebinthifolia and E. uniflora showed distinct responses in growth and leaf gas exchange. Neither enzymatic contents nor oxidative reduction showed any difference between the species. The restriction of Cu in roots appears to be the principal protective mechanism against Cu phytotoxicity, preventing negative effects on the physiological and biochemical status of the species. S. terebinthifolia shows potential as a Cu phytostabilizer.