Nutritional, Physiological, and Enzymatic Responses of Native Grasses from the Pampa Biome Cultivated Under Excess Zinc

Some soils in Brazil are contaminated with zinc (Zn). Even though it is an essential micronutrient, Zn, when in excess, harms plant growth. The Pampa biome has a great diversity of grasses. However, few studies have evaluated the growth potential and physiological and biochemical responses of these plants to excess Zn. The study aimed to evaluate, physiological point of view, the native grass species of the Pampa biome most tolerant species to excess Zn. The grass species of the Pampa biome used in the experiment were Andropogon lateralis, Axonopus affinis, Paspalum plicatulum, and Paspalum notatum. Three Zn doses were added to the solution, corresponding to 2 μM (original concentration of the nutrient solution), 150, and 300 μM of Zn in the form of ZnCl₂ for the cultivation of the four grasses. The increase in Zn availability increased the photosynthetic rate in the four species. Andropogon lateralis increased shoot and root dry matter production with increasing Zn concentration in solution. Andropogon lateralis increased phosphorus (P) retention in the root system, contributing to the increase of Zn in the roots. Axonopus affinis does not reduce its shoot growth when faced with increased Zn levels. Zn translocation when exposed to intermediate Zn levels. In Paspalum Notatum, antioxidant enzymatic activity is induced in response to excess Zn. Paspalum plicatulum absorbs a high concentration of Zn in the shoot. Andropogon laterallis was the only plant that showed an increase in biomass when grown in a higher dose of Zn.