Nitrogen fixation is the conversion of nitrogen gas from a mostly unusable form to a form that can be used by plants. The conversion of dinitrogen gas through to ammonium is carried out in the nodules of clover plants by bacteria called rhizobia. There are other forms of nitrogen fixers, such as kōwhai trees – they also have bacteria in root nodules that can convert dinitrogen into nitrogen that can be used by plants.
Image shows rhizobia nodules attached to roots of Vigna unguiculata.
