GROWTH AND NITROGEN ASSIMILATION IN NODULES IN RESPONSE TO NITRATE LEVELS IN VICIA-FABA UNDER SALT STRESS

This study analyses the effects of salt on the effective symbiosis of faba bean (Vicia faba L, var. minor cv. Alborea) and salt-tolerant Rhi zobium leguminosarum biovar. viciae strain GRA19 grown with two KNO3 l evels (2 and 8 mM). The addition of 8 mM KNO3 to the growth medium inc reases plant tolerance to salinity even with a concentration of 100 mM NaCl. This KNO3 level in control plants reduced the N-2 fixation. For 2 and 8 mM KNO, the plants treated with NaCl reduced N-2 fixation to identical values. The activity of the enzymes mediating ammonium assim ilation in nodules (GS, NADH-GOGAT and NADH-GDH) was decreased by high KNO, levels. The results show that NADH-GOGAT activity was more marke dly inhibited than was GS activity by salinity, therefore NADH-GOGAT l imits the ammonium assimilation by nodules in Ii. faba under salt stre ss. The total proline content in the nodule was not related to salt to lerance and thus does not serve as a salt-tolerance index for V. faba.