Ecophysiological constraints and strategies of Mucuna pruriens grown in mine tailings from the Fundão dam
Photosynthesis; Mn toxicity; Fe/Mn ratio; Ecotoxicology
In November 2015, the largest Brazilian iron mining disaster occurred in Mariana, MG, Brazil. Our aim wasto evaluate physiological alterations and limiting factors of growth in Mucuna pruriens cultivated in tailings and its potential for revegetation of impacted areas. Five new growth substrates were prepared by mixing different volumes of pure iron ore tailings from the Fundão dam with a fertilesoil-substrate. Different physicochemical properties and mineral composition of growth substrates were evaluated. In plants, wealso evaluated the mineral composition and physiological characteristics such as gas exchange, chlorophyll a fluorescence, carbohydrate and proline content, dry mass and superoxide dismutase activity. The most contrasting results were observed comparing the control and pure tailings treatment, with a trend of intermediate results for theother treatments (25-75% tailings). These trends are related to the low fertility in herent totailings and to high concentrations of Mn found in the substrates and leaf tissues of the plants. Mn likely impaired Fe acquisition in leaves and disturbed physiological processes, as reported by previous Mn phytotoxicity studies. Our results demonstrated that M. pruriensis a promising and relevant species to be included in revegetation efforts in areas affected by the Fundão dam tailings.