Nitrate, nitrate reduction and organic nitrogen in plants from different ecological and taxonomic groups of Central Europe.

48 plant species of the families Asteraceae, Chenopodiaceae, Ericaceae, Fabaceae, Lamiaceae, Polygonaceae and Urticaceae were investigated in 14 natural habitats of Central Europe having different nitrate supplies, with respect to their nitrate content, nitrate reductase activity (NRA) and organic nitrogen content. Plants that were flowering were selected where possible for analysis. The plants were subdivided into flowers, laminae, petioles+shoot axes and below-ground organs. Each organ was analyzed separately. Differences among species were found for the three variables investigated. Apart from the Fabaceae, which had particularly high concentrations of organic N, these differences reflect mainly the ecological behaviour, i.e. high nitrate and organic N contents and NRA values per g dry weight were found in species on sites rich in nitrate, and vice versa. Nitrate content, NRA and organic N content were correlated with "nitrogen figures" of Central European vascular plants defined by Ellenberg (1979). By use of regression equations this correlation was tested with species from other systematic groups. Some species were attributed with calculated "N figures" for the first time.