The association of bacteria with plants has been studied as a possible emerging technology for phytoremediation of contaminants, including herbicides, which pose as a threatening to environmental quality due to their recalcitrance. The aim of this study was to assess the tolerance of dwarf mucuna (Stizolobium deeringianum Bort) and black mucuna (Stizolobium aterrimum Piper & Tracy) inoculated and uninoculated with Rhizobium to the herbicide atrazine. The treatments were: plants with inoculant + 0.1 g/m², 0.2 g/m² atrazine, and without atrazine (T1, T2 and T3, respectively), plants without inoculant + 0.1 g/m², 0.2 g/m² atrazine and without atrazine (T4, T5 and T6, respectively). The experiment was arranged in a completely randomized design, with three replications. Plants were grown in a greenhouse for 50 days and the variables germination, survival, number of nodules, height, green/dry biomass of the aerial part were evaluated. In the treatments with inoculants, the germination percentage of bioindicator plants (Bidens pilosa L.) was also evaluated. Black mucuna and dwarf mucuna showed greater tolerance to the herbicide when associated with Rhizobium. The survival rates of black mucuna at the doses 0.1 and 0.2 g/m² atrazine (T1 and T2) were 34 and 24% higher than those observed at the same doses, but without the inoculant (T4 and T5). For dwarf mucuna, T1 and T2 were 17 and 8% higher than T4 and T5, respectively. The average heights of dwarf mucuna in T1, T2 and T3 were higher than in T4, T5 and T6, reinforcing the importance of the symbiont to the herbicide resistance. The results found for the variables height, green and dry biomass for black mucuna were not significantly different among the treatments with and without inoculant, showing a natural resistance to atrazine and the possibility of acting as a remediation plant. The germination of B. pilosa indicates a possible degradation of atrazine in the soil by both mucuna species inoculated with Rhizobium sp.
Black mucuna; dwarf mucuna; degradation; herbicide; endosymbiont bacteria
