Biological nitrogen fixation is a crucial biochemical process in plants, through which atmospheric nitrogen (N₂), which is chemically inert and unavailable for direct use by most organisms, is converted into ammonia (NH₃) or related nitrogenous compounds that plants can assimilate. Nitrogen is an essential element for the synthesis of amino acids, proteins, nucleic acids, and other cellular constituents, making nitrogen fixation vital for plant growth, development, and productivity. This process is carried out by a specialized group of microorganisms, including free-living bacteria, symbiotic bacteria, and cyanobacteria. Symbiotic nitrogen fixation primarily occurs in legumes, such as peas, beans, and clover, through a mutualistic association with bacteria of the genus *Rhizobium*. The bacteria colonize root hairs of host plants, inducing the formation of root nodules, which are specialized structures that provide an anaerobic environment favorable for nitrogenase activity. Inside these nodules, *Rhizobium* bacteria convert atmospheric nitrogen into ammonia using the nitrogenase enzyme complex. Nitrogenase is highly sensitive to oxygen; therefore, leghemoglobin, a plant-synthesized oxygen-binding protein, regulates oxygen concentration in nodules to ensure optimal enzyme activity while allowing respiration to occur. The ammonia produced is rapidly assimilated