Answer:
Nitrogen Fixation.
Step-by-step explanation:
This is known to happen by mutualism between the nitrogen fixing bacteria and roots of leguminous plants. The bacteria enter roots of leguminous plants and cause certain root cells to divide, forming nodules. The bacteria live and multiply in these nodules. They convert the free nitrogen in the soil to organic compounds, which are used by the plant for their metabolic activities. In return, the plant provides the bacteria with shelter and organic nutrients such as sugar and vitamins