Physiological and biochemical changes in tree seedlings in an urban forest soil contaminated with copper

Abstract

Context Soil pollution by heavy metals is a worldwide environmental concern. Owing to their proximity to anthropogenic emission sources, urban forest fragments are highly affected by the excessive input of heavy metals into the soil.Objectives This study aimed to assess the physiological and biochemical responses of two native Brazilian Atlantic Forest Schinus terebinthifolia Raddi (pioneer species) and Eugenia uniflora L. (non-pioneer species), when cultivated in soils contaminated with Cu. Methods 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 copper stress, while the enzymatic (superoxide dismutase) and nonenzymatic (ascorbic acid and glutathione) antioxidants were quantified to assess the biochemical responses of the species. Results 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. The species showed neither difference in enzymatic contents nor oxidative reduction. Conclusion The restriction of copper in roots appears to be the principal protective mechanism against copper phytotoxicity, preventing negative effects on the physiological and biochemical status of the species. S. terebinthifolia shows potential as a Cu phytostabilizer, while the E. uniflora has potential as a Cu phytoextractor.