Nitrogen metabolism of Plantago lanceolata as dependent on the supply of mineral nutrients

Various aspects of nitrogen metabolism of Plantago lanceolata L., a grassland species from a relatively nutrient poor habitat, were investigated under high nutrient conditions or low nutrient conditions. In addition the responses after switching the plants from high nutrient conditions to low nutrient conditions and vice versa were studied. The activities of nitrate reductase (NR), glutamate dehydrogenase (GDH) and glutamine synthetase (GS) were determined. In the roots they were correlated with the level of the nutrient supply. Not only NR but also GDH and GS increased upon a switch from low nutrients to high nutrients and decreased upon a switch from high nutrients to low nutrients. Reduced nitrogen content of both roots and shoots was also correlated with the nutrient supply and changed rapidly after a switch. The flexibility of the nitrogen metabolism of Plantago lanceolata is discussed in relation to its ecological habitat.