Abstract
Faba bean cv. Giza 3 was grown in hydroponic cultures and inoculated with Rhizobium leguminosarum bv. viceae TAL 1402. Salinity levels at 40, 80 and 120 mM NaCl were applied at transplanting and inoculation. The highest level of salinity level (120 mM) significantly suppressed nodulation, nitrogenase activity and plant growth. This salinity level also significantly decreased the concentrations of macro and micro nutrients in faba bean leaves. X-ray microanalyses of nodules under high levels of NaCl indicate that Ca, K, Mg and S were lower in the infected and uninfected cells of faba bean nodules than control ones, whereas, Na and Cl were higher. Nitrogen content of nodules was significantly higher in plants treated with high salinity levels than nonsalinized ones. However, the N content of shoots was lower than the controls, The inhibition of nitrogenase activity at high levels of salt stress could be explained in terms of product inhibition of the enzyme as an efficient feedback regulation mechanism, The X-ray microanalysis results revealed that the N export from nitrogen-fixing cells is sensitive to salinity and is controlled by element distribution in nodules.