摘要：We characterized and compared the use of nitrate (N-NO3−), 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-NO3−
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-NO3− content in leaves and xylem sap of
each species. We measured N-NO3− and N-NH4+ content in
the soil. The results for Cgl showed an N-NO3− content of xylem
sap that met the demand of NRA and were correlated with inorganic soil
nitrogen, showing the responsiveness of species to N-NO3−. Hco
was verified as less responsive to assimilation and high N-NO3−
content in leaves. The species Ima showed an intermediate behaviour, which
suggests the possibility of use of other nitrogen forms. The
ecophysiological behaviours of the plants were related to the seasonal
variation and indicate that these plants use strategies with different
responsiveness to the use of soil N-NO3−. 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.
