Manganese mitigates the effects of excess iron on Zeyheria tuberculosa (Vell.) Bureau ex Verl. plants

Mining plays a crucial role in the Brazilian economy. However, this activity generates waste contaminated with high concentrations of iron and manganese. Native species, such as Zeyheria tuberculosa, are a promising solution for revegetating these areas. Native plants are a promising solution for revegetating these areas, especially ruderal species such as Zeyheria tuberculosa, which has low nutritional requirements and high survival rates across a range of soil types. Therefore, this study aimed to assess how metabolism is affected when young Z. tuberculosa plants are treated with excess iron (Fe) and manganese (Mn). The plants were cultivated in the sand and irrigated with different nutrient solutions: a complete nutrient solution (control), excess iron (0.160 mM), excess manganese (0.327 mM), and excess iron and manganese (0.160 and 0.327 mM). Excess iron led to symptoms of toxicity, as evidenced by a reduction in root length, decreased pigment content and photosynthetic efficiency, and lower carbohydrate levels. Similar responses were not observed in treatments with excess manganese. In plants exposed to high concentrations of both iron and manganese, there was a reduction in iron absorption and an increase of manganese, thus reducing the iron toxicity. In addition, there were increased nitrogen content, free amino acids, and enzymatic activity within the antioxidant system, while levels of proteins and soluble and reserve carbohydrates were decreased. Excess manganese proved to be less harmful to Z. tuberculosa plants, and it even mitigated the toxic effects induced by excess iron across most of the physiological parameters assessed. This suggests that this species holds promising potential for soil recovery in contaminated areas containing iron and manganese waste.