Abstract: | This study analyses the effects of salt on the effective symbiosisof faba bean (Vicia faba L. var. minor cv. Alborea) and salt-tolerantRhizobium leguminosarum biovar. viciae strain GRA19 grown withtwo KNO3 levels (2 and 8 mM). The addition of 8 mM KNO3 to thegrowth medium increases plant tolerance to salinity even witha concentration of 100 mM NaCl. This KNO3 level in control plantsreduced the N2 fixation. For 2 and 8 mM KNO3 the plants treatedwith NaCl reduced N2 fixation to identical values. The activityof the enzymes mediating ammonium assimilation in nodules (GS,NADH-GOGAT and NADH-GDH) was decreased by high KNO3 levels.The results show that NADH-GOGAT activity was more markedlyinhibited than was GS activity by salinity, therefore NADH-GOGATlimits the ammonium assimilation by nodules in V. faba undersalt stress. The total proline content in the nodule was notrelated to salt tolerance and thus does not serve as a salttoleranceindex for V. faba. Key words: Glutamate synthase, glutamine synthetase, N2 fixation, nitrate, salinity |