Effects of ammonium levels on growth and accumulation of antioxidative flavones of the submerged macrophyte Ceratophyllum demersum

Abstract Field data on the occurrence of the common and cosmopolitan submerged macrophyte Ceratophyllum demersum in relation to the water ammonium content were compared with the response of the plants to different ammonium treatments performed in the laboratory. Ammonium concentrations above 10 µM in the monitored area were found to be a strong limiting factor on the presence of C. demersum in water bodies. On the other hand, no adverse effect of nitrate was observed. In short-term laboratory experiments, the plants grew well even at 100 µM ammonium at pH 7.5, but higher concentrations affected the plant. Laboratory experiments showed that the accumulation of flavonoids with antioxidant properties was induced by ammonium. The detailed LC/MS analysis of the major flavonoids showed that the most abundant compound was tricetin present mainly as a monoglycoside in crude extracts. Luteolin, selgin, apigenin, tricin and chrysoeriol glycosides were also present in considerable amounts. Tricetin, a flavonoid having strong antioxidative properties, was most induced by higher ammonium levels. At high ammonium concentrations, plant tissues exhibited notable damage and the production of antioxidants declined.