The plants need nitrogen for their growth. In atmosphere plenty of nitrogen is there but plants cannot use it directly. They need nitrogen in a soluble form. The Rhizobium a kind of bacteria which lives in the roots of gram, peas, moong, beans and other legumes. It can take atmospheric nitrogen and convert it into usable form. Rhizobium provides nitrogen to plants, in return the plants provide food and shelter to the Rhizobium. Thus they have a symbiotic relationship. This is of great significance for the formers.
