Alternative tools, such as the manipulation of mineral nutrition, may affect secondary metabolite production and thus the nutritional value of food/medicinal plants. We studied the impact of nitrogen (N) nutrition (nitrate/NO3(-) or ammonium/NH4(+) nitrogen) and subsequent nitrogen deficit on phenolic metabolites and physiology in Matricaria chamomilla plants. NH4(+)-fed plants revealed a strong induction of selected phenolic metabolites but, at the same time, growth, Fv/Fm, tissue water content and soluble protein depletion occurred in comparison with NO3(-)-fed ones. On the other hand, NO3(-)-deficient plants also revealed an increase in phenolic metabolites but growth depression was not observed after the given exposure period. Free amino acids were more accumulated in NH4(+)-fed shoots (strong increase in arginine and proline mainly), while the pattern of roots' accumulation was independent of N form. Among phenolic acids, NH4(+) strongly elevated mainly the accumulation of chlorogenic acid. Within flavonoids, flavonols decreased while flavones strongly increased in response to N deficiency. Coumarin-related metabolites revealed a similar increase in herniarin glucosidic precursor in response to N deficiency, while herniarin was more accumulated in NO3(-)- and umbelliferone in NH4(+)-cultured plants. These data indicate a negative impact of NH4(+) as the only source of N on physiology, but also a higher stimulation of some valuable phenols. Nitrogen-induced changes in comparison with other food/crop plants are discussed.
Keywords: Antioxidants; Flavonoids; Mineral nutrition; Nitrogen deficiency; Phenolic metabolism.
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