Metallic elements in plants: bioaccumulation, phytoremediation potential and physiological responses

Abstract

Pollution caused by metallic elements in the environment is becoming increasingly problematic worldwide. In the current work, several aspects of the metallic elements in plants were investigated, including the accumulation in species affected by an environmental disaster involving the disruption of a mining tailing dam; the physiological responses and phytoremediation potential of the aquatic macrophyte water lettuce (Pistia stratiotes) subjected to excess iron (Fe) and manganese (Mn), and combinations of Fe, Mn, and arsenic (As); and, finally, the in vivo monitoring of As-induced responses in Arabidopsis thaliana plants. We found a concerning enrichment of metal accumulation, especially for Fe and Mn, in the plant species evaluated in affected areas by mining tailings. Considering the spreading potential of contamination in aquatic environments, water lettuce plants, which are often used in phytoremediation studies, were tested for removal of excess Fe and Mn, along with the association with As. The plants displayed a great accumulation of Fe, mainly trapped in roots, whereas Mn was hyperaccumulated in shoots and roots. Accumulation of Mn was observed especially in the apoplast, avoiding major impairments of physiological processes. In presence of As, the plants displayed root loss as an acclimation response, followed by re-emission of the organs. Nonetheless, the specimens were able to maintain a high accumulation of the pollutants, supplied isolated or in association, demonstrating phytoremediation potential in multi- contaminated environments. Furthermore, the in vivo measurements using genetically-encoded biosensors showed intriguing stability of Mg-ATP 2− levels upon short-term arsenate (AsV) exposure. We also observed that the depletion of the GSH pool is the most likely cause of glutathione redox potential (E GSH ) oxidation. The findings presented here emphasize the importance of continuing to monitor metal-contaminated areas, as well as exposing alternatives for phytoremediation of aquatic environments and providing new insights into plant metabolism in response to pollutants. Keywords: Aquatic plants – Pollution effect. Aquatic plants – Heavy metal effects. Pistia stratiotes. Heavy metals. Aquatic plants – Metabolism.