Abstract.We characterized and compared the use of nitrate (N-NO − 3 ), in three recognized pioneer and secondary tropical species, analyzing their relationships with the availability of inorganic nitrogen in the soil of a riparian forest. We tested the hypothesis that pioneer species of the ecological succession (Cecropia glaziovi -Cgl) would be more responsive to N-NO − 3 available and would have high nitrate reductase activity (NRA) in leaves while secondary species (Inga marginata -Ima and Hymenaea courbaril -Hco) would have less responsiveness and would have lower levels of this enzyme on its leaves. We evaluated, tested and compared the NRA and N-NO . In this sense and considering that these species are typically used in ecological restoration projects in Brazil, the knowledge of a strategy for nitrogen use specific to each of them can assist in choosing the species appropriate to the edaphic conditions of the environment.

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