The root nodules are formed after the symbiotic bacteria Rhizobium invades root hairs.Legume photosynthesis provides the energy that drives the BNF symbiosis.

• 根瘤是共生细菌（根瘤菌属）侵入根毛后形成的，豆类作物光合作用为共生固氮共生体提供能量。