Bacteria called as Rhizobium present in the root nodules of leguminous plants fix nitrogen. It is a soil bacterium that fix nitrogen from the atmosphere once it is contained inside the leguminous plant roots. Nitrogen fixation can not be performed independently. Therefore, rhizobium needs a host of plants. Rhizobium is a key nitrogen source for agricultural soils, including those in arid areas. They turn the dinitrogen into ammonia. Ammonia, being poisonous, is absorbed easily into organic compounds.
- Plants cannot fix atmospheric nitrogen on their own, but require it in some form to make amino acids and proteins.
- Rhizobium multiplies within the cortex cells and forms nodules, and the nodules turn pink as the nitrogen fixation starts.