First, all games start with atmospheric nitrogen which is composed of about 78% of the total atmosphere. But there is a problem plants and animals can’t use nitrogen directly for the atmosphere. That is why we need a mechanism by which plants convert atmospheric nitrogen into nitrogenous compounds.
So, in this, the main hero root nodules and Rhizobium play an important role. Root nodule is the structure present on the root which forms symbols with nitrogen-fixiting bacteria.
The main work of these nitrogen-fixation bacteria is to convert nitrogen into nitrogenous compounds( like ammonia, nitrates, etc.,)