Figure 17.4 Root nodules that contain Rhizobium bacteria. Legumes such as this bean plant can enter into a mutualistic relationship with Rhizobium bacteria. The plant provides the bacteria with sugars from photosynthesis and a root nodule in which the bacteria can grow. In return, the bacteria convert atmospheric nitrogen to ammonia, a form of nitrogen that the plant can use.
Photo by Nigel Cattlin/Science Source.