Induction of phenolic metabolites and physiological changes in chamomile plants in relation to nitrogen nutrition

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.