Abstract: The aim of this experiment was to investigate the responses caused by progressive water stress and the necessary time for have biochemical and physiological changes of Vigna unguiculata (L.) Walp. cv: manteguinha during the vegetative phase. Leaf Relative Water Content (LRWC), Nitrate Reductase Activity (NRA), free proline, total soluble carbohydrates, free amino acids and total soluble proteins were quantified. The plants under the control treatment maintained stable variables; however, those under water stress suffered an increase of 97.3% in proline due to osmotic adjustment, increase of 78.4% in free amino acids, caused by the break down of proteins by protease enzymes, increase in total carbohydrates by 94.2% due to a decrease in the photosynthetic capacity and low synthesis of sucrose used for exporting this solute. There was a decrease in 25.7% of the leaf relative water content in virtue of low water availability in the soil, reduction of 43.8% in Nitrate Reductase Activity (NRA) due to the regulation of this enzyme being induced by its substratum and 47.3% of total proteins due to the paralyzation of protein and proteolytic protein degradation, being maximized the variations in the parameters evaluated according to the increase in the period the plants were exposed to water stress. Physiological changes can be carried out in only a few days. However, biochemical responses should be evaluated starting at 4 days under water restriction.