Efectos del estrés hídrico en la fijación simbiótica de nitrógeno en la asociación Phaseolus vulgaris L. - Rhizobium leguminosarum bv. phaseoli = Water stress and its effect on symbiotic fixation of nitrogen in an association Phaseolus vulgaris L. - Rhizobium leguminosarum bv. phaseoli

Tratamientos que no fueron sometidos a estrés hídrico presentaron promedios superiores con relación a aquellos que estuvieron bajo estrés para las variables peso fresco de la zona radical (26.72 g), pesos fresco (47.92 g), seco (11.81 g) y área (1086.7 cm2) de la zona foliar, número (8.9) y peso seco (3.8 g) de vainas. La proporción zona radical/zona foliar mostró promedios superiores en los tratamientos con estrés hídrico en relación los no estresados. De acuerdo con las interacciones entre el estrés hídrico y la inoculación con Rhizobium, se mostró un nivel menor de resistencia estomática y de transpiración, lo cual podría sugerir que esta asociación simbiótica puede ser un mecanismo regulador de la respuesta al estrés

This study was carried out in order to evaluate the behavior of the ICA Cerinza. bean cultivar symbiosis with three Rhizobium strains, under optimal water supply and under water stress. According to the results, the effects of inoculated and uninoculated treatments with Rhizobium, over some variables such as fresh root weight, exhibited the highest average value for ICA-P19 strain inoculated treatment and the highest average value of number and dry weight of nodules for ICA - P6 strain inoculated treatment. Foliar nitrogen concentration was higher than that of N-test (70 ppm), followed by ICA - P6 strain inoculated treatment, and also showed higher average values of nitrogen concentration in pods. Stomatal resistance was higher in N-test (20 ppm) when compared to other treatments. Nitrogen and phosphorus content and concentration in leaf and pods, were affected by water stress, showing higher average concentrations, contrarily to the total contents, being higher in no water stress conditions. Treatments under no water stress showed higher average values of fresh root weight than those under stress (26-72 g), fresh weight (47.92 g), dry weight (11.81 g) shoot area (1086.7 cm2), pod number (8.9) and pod dry weight (3.8 g). Root/shoot ratio averages were superior in water stressed treatments. According to interactions between water stress and Rhizobium inoculation in plants, it was shown a lower stomatal resistance and transpiration values, which could suggest that this symbiotic association can be a regulation mechanism for water stress response.