What transformation occurs to nitrogen in anaerobic conditions?

In anaerobic conditions, the transformation of nitrogen primarily occurs through the process of denitrification, where nitrate (NO3-) is converted into nitrogen gas (N2) or, to a lesser extent, nitrous oxide (N2O). This process is facilitated by specific denitrifying bacteria that thrive in low-oxygen environments. During denitrification, these bacteria utilize nitrates as a terminal electron acceptor in their metabolic processes, effectively reducing nitrates to nitrogen gas, which is then released into the atmosphere.

This transformation plays a crucial role in the nitrogen cycle, as it helps to balance nitrogen levels in the environment and prevents the accumulation of nitrates, which can lead to issues like nutrient pollution in water bodies. By converting nitrates into nitrogen gas, denitrification also contributes to the return of nitrogen to its atmospheric form, maintaining ecological balance.

The other options do not accurately describe transformations of nitrogen under anaerobic conditions. Nitrogen fixation, for instance, typically occurs in aerobic environments and involves the conversion of atmospheric nitrogen into ammonia. The absorption of nitrogen directly by plant roots does not relate to anaerobic conditions and pertains primarily to nitrate and ammonium uptake in soil. The transformation into solid compounds does not reflect a common process for nitrogen under