In nature, how is nitrogen of the atmosphere made available for the plant growth ?

Atmospheric nitrogen (N2) is highly inert due to its triple covalent bond and is inaccessible to most organisms directly [t1, t2]. In nature, it is made available for plant growth primarily through biological nitrogen fixation (BNF), a process carried out by specialized prokaryotes known as bacteria [t1, t4]. These include symbiotic bacteria like Rhizobium, which form nodules on the roots of leguminous plants, and free-living bacteria such as Azotobacter and Clostridium [c1, c2, t3]. These bacteria utilize the enzyme nitrogenase to convert atmospheric nitrogen into ammonia (NH3) or nitrates, which plants can readily assimilate for protein and nucleotide synthesis [c5, t1, t6]. While fungi and earthworms play vital roles in nutrient cycling and soil structure, they do not possess the metabolic pathways to fix atmospheric nitrogen [c3, t5]. Viruses are non-cellular entities and do not participate in nitrogen fixation [t5].

Sources

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