Glyphosate Effect on Nitrogen Fixation and Metabolization in RR Soybean

To evaluate under controlled temperature conditions, nutrition and water supply, the influence of glyphosate on nitrogen fixation capacity in Roundup Ready (RR) soybean, BRS Valiosa Roundup Ready. Commercially available seeds were sown in pots containing vermiculite and washed sand (1-1) and after germination, the seeds were inoculated with Bradyrhizobium sp. and kept in nutrient solution without nitrogen, in greenhouse, with temperature control to 27 ºC without photoperiod control, at UNESP, Ilha Solteira, SP. At the vegetative stage, glyphosate was applied at a concentration of 1.8 mg glyphosate/plant once a week. There were two harvests- after 15-21 days after herbicide application, and at reproductive stage. The chlorophyll content in leaves was analyzed and the organs were separated (leaves, roots and nodules) for extraction and quantitation of nitrogenous compounds, in addition to the enzyme allantoinase activity analysis (in vitro) and nitrogenase activity (in vivo). Nodules were counted and weighted. Means were compared by 5% Tukey’s test. It was observed that the application of glyphosate in RR soybeans moderately affected N fixation and assimilation. There were no drastic metabolic changes for the aminoacids, proteins, chlorophylls and ureides in RR soybean treated with glyphosate.