Interactions between Phaseolus vulgaris cultivars and Rhizobium strains in nitrogen fixation and transport

Abstract

One experiment was performed, under greenhouse conditions, using five cultivars of Phaseolus vulgaris L. and six strains of Rhizobium leguminosarum biovar phaseoli to evaluate the nitrogen fixation and transport in the plants. Both cultivars and strains affected significantly the dry weight and total P4 of leaves, stems and pods; nodule dry weight; nodule efficiency (mg N. g nod^-1); nitrogenize activity; H₂evolution by the nodules; relative efficiency (RE); N concentration and rate of N translocation in the xylem sap and percentage of the N of the xylem sap as ureides. The parameters (estimated at flowering time, 35 days after germination) that showed best correlations with total N of pods at 50 days were: RE (0.872**), rate of N translocation in the xylem sap (0.949**) and percentage of N as ureides in the xylem sap (0.907**). A positive correlation was found between RE and percentage of N as ureides (0.903**), and this can be best explained in terms of a relationship between H₂ metabolism and ureide metabolism.