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), Helianthemum squamatum (Hsq), Helianthemum alypoides (Ha), and Lepidium subulatum (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 greatest stimulation of nitrogen metabolism, with the lowest levels of NO3-, highest NR and NiR activities, and highest concentrations of nitrogenous compounds, a possible determining factor in this trend being the lowest Ca concentrations registered for this species. On the other hand, this species also presented the highest proline concentrations. Possibly for the highest nitrogen metabolism and the highest concentrations of proline, this species is the most prevalent of the five plants in the study zone. Finally, the opposite trend was found in the species Ha and Hsq.