Nitrogen metabolism of Plantago major ssp. major as dependent on the supply of mineral nutrients

Various aspects of the nitrogen metabolism of Plantago major L. ssp. major, a grassland species from a relatively nutrient‐rich habitat, were investigated with plants that were grown in nutrient‐rich and nutrient‐poor culture solutions. In addition the influence of a change in the nutrient supply, both from high to low and from low to high nutrient conditions was studied. The data on P. major major showed that the activities of nitrate reductase (NR) and the reduced nitrogen content were all rather independent of the nutrient supply. These findings are in contrast with those of P. lanceolata, a grassland species from a relatively nutrient‐poor habitat, where both the activities of NR, GDH and GS and the reduced nitrogen content were correlated with the level of the nutrient supply. The rigidity of the nitrogen metabolism of P. major major may be of advantage if the nutrient supply is limited only for relatively short periods.