Potencial de leguminosas colonizadas por micorrizas arbusculares para revegetação de áreas de mineração de manganês

Abstract

Excess manganese (Mn) in the soil can cause toxicity to plant species. Strategies that mitigate this type of impact are fundamental in a revegetation process. The objective of this study was to: i) test the efficiency of different arbuscular mycorrhizal fungi (AMF) in promoting the development and tolerance of legume species in a soil with increasing levels of manganese and ii) use scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) to investigate the capacity of AMF structures to accumulate Mn. For this, three experimental tests were conducted using the species: Mimosa caesalpiniaefolia, Leucaena leucocephala and Acacia mangium. The experimental design for each trial was completely randomized in a 4x4 factorial arrangement, considering: four doses of Mn (0; 100; 200 and 400 mg kg-1) and four inoculation treatments (Control – not inoculated; Claroideoglomus etunicatum; Acaulospora scrobiculata; Diversispora sp.). It was determined the shoot and root dry matter mass, content of phosphoru in the shoot and Mn in the shoot and root, soil pH after cultivation, leaf toxicity percentage by Mn, AMF spore density in soil, mycorrhizal colonization and Mn on the surface of AMF spores, through SEM and EDS. The assays showed different behavior of the leguminous species as a function of the increase of Mn doses and inoculation with AMF. From the results obtained, we can conclude that, excessive concentrations of Mn in the soil cause phytotoxicity and inhibit the development of legume species. AMF inoculation attenuates the Mn-induced toxicity and maximizes the development of legume species. The benefits provided by AMF depend on the host plant and the concentration of Mn in the soil. AMF spores accumulate Mn on its surface, acting as a biological barrier to decrease phytotoxicity and increase tolerance of leguminous species to Mn. The efficiency of this mechanism is dependent on the AMF species and the host plant. When considering the tolerance of legume species based on their biomass and the percentage of Mn toxicity, the A. mangium and M. caesalpiniaefolia species, associated to the AMF Diversispora sp. and C. etunicatum, respectively, present a higher tolerance to high concentrations of Mn in the soil, making them, in this study, the most suitable for future revegetation practices of mining areas with excess Mn.