Consequences of the water deficit on water relations and symbiosis in Vigna unguiculata cultivars

The study aimed at evaluating and comparing changes provoked by the water deficit on water relations and nitrogen fixation in two Vigna unguiculata cultivars, as well as at indicating which cultivar is more tolerant under water deficiency. The experimental design used was entirely randomized in factorial scheme, with 2 cultivars (Pitiuba and Perola) and 2 water regimes (control and stress). The parameters evaluated were the leaf relative water content, stomatal conductance, transpiration rate, nodule number, nodule dry matter, nitrate reductase enzyme activity, ureide concentration and leghemoglobin in nodule. The stomatal conductance of the Pitiuba and Perola cultivars under water deficit were 0.20 and 0.01 mmol H2O/m(2)/s, respectively. The nitrate reductase activity of the plants under stress was significantly reduced in both cultivars. The leghemoglobin in the Pitiuba and Perola cultivars under water stress had the concentrations of 58 and 41 g/kg dry matter, respectively. The parameters investigated in this study suggest that the Pitiuba cultivar under water deficit suffers from smaller changes, when compared with Perola cultivar.