How do native grasses from South America handle zinc excess in the soil? A physiological approach

The excess of zinc (Zn) in vineyard soils promotes grape yield restraints. Thus, it is urgent to set up sustainable strategies aiming at decrease phytotoxic potential of Zn for crops. The selection on biochemical and physiological bases of wild plants to intercrop with perennial ones might be the key step to identify and characterize unknown mechanisms of metal tolerance in these plant species. This study aimed to evaluate the physiological and biochemical responses of native grasses of South America exposed to high Zn concentrations in the soil. The soil was sampled in a non-anthropized area and it was incubated with the following Zn amounts: 0, 30, 60, 120, or 180 mg Zn kg-1 soil. The native grass species considered were: Axonopus affi nis, Paspalum notatum, and Paspalum plicatulum. Dry mass accumulation, the nutritional composition of plants, photosynthetic parameters, antioxidant enzyme activities, and oxidative stress indicators have been evaluated. A. affinis specie increased photosynthetic rate, pigments concentrations, and biomass production as Zn increased in soil. While it did not enhance the reactive oxygen species, and did not show lipid peroxidation under Zn excess. On the other hand, species P. plicatulum and P. notatum were more sensitive to Zn excess in the soil, showing oxidative injuries, which reduced plant growth. Hence, results show that A. affinis possess the physiological and biochemical features for controlling the Zn availability in the soil supporting, thus, the idea of its effective use in agronomical strategies for containing the Zn toxicity problem.