Nitrogen has a wide range of valence states in compounds, which may be used in plant metabolism.
Although some compounds have oxidation-reduction states of +7, as in pernitric acid, plant
metabolites have oxidation- reduction states ranging from +5 (nitric acid, nitrate) to -3 (ammonia,
ammonium) (4). Organic, nitrogen-containing compounds are at the oxidation-reduction state of
nitrogen in ammonium (-3). Biologically important organic molecules in plants include proteins,
nucleic acids, purines, pyrimidines, and coenzymes (vitamins), among many other compounds.