The assimilation of nitrogen in plants is affected by the drought and also by the waterlogged soil, and abserved dramatic reductions in the activity of nitrate reductase,from smaal decreases in water potencial and in the absence of oxygen in the soil macro and micropores. In this context, the aim this work was to asses the presence or not of nitrate reductase activity in gabiroba plant and to verify the affects of different water availability in the soil on the activity os this enzyme in order to verify the possible strategies for survival. The experimente was carried out under natural vegetation.Established and three conditions of water availability: water budget deficit,field capacity and hipoxia in seven different times (before undergoing treatmente)12 hours, 24 hours, 1 weeks, 3 weeks and 4 weeks after submission of the treatments. The activity of nitrate reductase was determined in shoots and roots of plants,using the in vivo that reflects and potential activity of nitrate reductase in situ. Patients were also evoluated agronomic traits in the studied treatments. Plants Campomanesia sp. present activity of nitrate reductase in leaf and root tissue. The activity of nitrate reductase is predominantly foliar. A availability of water affected the enzyme activity when compared to normal handling.Plants Campomanesia sp. showed greater tolerance of nitrate assimilation in drought conditions compared to conditions of flooding.