Nitrogen metabolism in five plant species characteristic of gypsiferous soils

Nitrogen metabolism has been studied in 5 species of plants characteristic of gypsum soils: Gypsophila struthium (Gs), Helianthemum syriacum (Hsy), He lianthemum squamatum (Hsq), Helianthemum alypoides (Ha), and Lepidium subul atum (Ls). Nitrate, nitrate reductase (NR), nitrite reductase (NiR), amino acids, proteins, proline, organic N, total calcium, and population density were analysed. Our results show Ls to be the species that presented the gre atest stimulation of nitrogen metabolism, with the lowest levels of NO., hi ghest NR and NiR activities, and highest concentrations of nitrogenous comp ounds, a possible determining factor in this trend being the lowest Ca conc entrations registered for this species. On the other hand, this species als o presented the highest proline concentrations. Possibly for the highest ni trogen metabolism and the highest concentrations of proline, this species i s the most prevalent of the five plants in the study zone. Finally, the opp osite trend was found in the species Ha and Hsq.