FIGURE 1.

Nitrogen transformations in soybean rhizosphere. Organic nitrogen in the nodule is mineralized into NH₄⁺ that will be transformed into N₂O through nitrification and denitrification processes. Soybean bradyrhizobia (blue) and other microorganisms contribute to the denitrification process. The N₂O formed is either emitted into the atmosphere (red) or further reduced to N₂ exclusively by soybean bradyrhizobia that produce N₂O reductase (N₂OR; blue). Nase, nitrogenase; NR, dissimilatory nitrate reductase; Nap, periplasmic nitrate reductase; NIR, dissimilatory nitrite reductase; NirK, Cu-containing nitrite reductase; NOR, nitric oxide reductase; cNor, c-type nitric oxide reductase. See text for more details.