Evaluation of growth and oxidative stress as indicative of salinity tolerance by the invasive tropical aquatic macrophyte tanner grass

In an estuary of a neotropical region located in Brazil, Urochloa arrecta occurs only in the area of freshwater. Nonetheless, information about the capacity of this population to invade areas considered inhospitable, i.e., saltwater, is scarce. In this sense, the aim of this study was to evaluate the effect of intermediate (20 ppt) and high (30 ppt) salinity on individuals from a population of U. arrecta located in the freshwater region of an estuarine ecosystem. Analyses of plant biomass, nitrogen, phosphorus, malondialdehyde (MDA) and hydrogen peroxide content were evaluated as possible indicators of tolerance to salt stress. Our results showed that salinity reduced growth and increased oxidative stress. However, under conditions of intermediate salinity, U. arrecta individuals showed a biomass gain greater than 60%, MDA content similar to that in freshwater, and higher nitrogen absorption and assimilation. We conclude that U. arrecta probably presents physiological adjustments that allow its survival at intermediate salinity. Thus, the ability of this species to expand in this area alerts to the importance of studies that seek to adopt policies for the control or management of the species in saline ecosystems.