Heavy-metal attack on freshwater side: Physiological defense strategies of macrophytes and ecotoxicological ops

Abstract

For many years, strong anthropogenic pollutions like heavy metals induce deep changes in all ecosphere compartments especially in streams where deleterious effects on aquatic plants are noted. Indeed, ionic interactions on whole plant surface and permanent replacement of metal pool lead to ecophysiological disruptions among freshwater macrophytes. To prevent from irreversible alterations, macrophytes develop a typical antioxidant systems (e.g., proteins, secondary metabolites, metabolic pathways) to protect intracellular components from reactive oxygen species and to preserve major biosynthesis pathways like photosynthesis. These macrophytes also accumulate solutes to cope with increasing external metal toxicity. Moreover, new anatomical features reducing water stress and leading to cell homeostasis can appear in leaves, as a double endodermis. Tolerance to heavy metals is an interesting feature of freshwater plants for understanding any adaptation and acclimation processes to highly ionic concentrated environments at the genetic level. Indeed, specific genes involved in the synthesis of molecular chaperones might be related to heavy-metal tolerance in macrophytes. Due to their metal sensitivity and bioaccumulation capabilities, these organisms appear essential in ecotoxicological studies like biomonitoring to manage natural habitats.