Effect of nitrogen nutrition on salt tolerance of Pisum sativum during vegetative growth

The influence of different nitrogen (N) forms on salt tolerance of Pisum sativum L. was investigated. Plants of the pea cultivar "Resal" were subjected to 0 (control) or 90 mM NaCl and one of the following nitrogen forms: 5 mM mineral N supplied as either NO3-, NH4+, or NH4NO3 or N supplied by biological N-2 fixation (inoculated with Rhizobium leguminosarum bv. viciae). Root and shoot biomass were determined 15, 30, 45, and 60 d after emergence, and Na+, K+, and Cl- concentrations were determined by capillary electrophoresis. Nitrogen sources induced significant differences in plant growth and in ion accumulation and distribution and in differentially affected salt tolerance. In the absence of salt, the largest biomass accumulation was obtained with NH4NO3. In the presence of NaCl, NO3--fed plants experienced less salt toxicity than plants Supplied with other N sources, as indicated by lower Na+ and Cl- and higher K+ concentrations in the shoot. The results also suggest that it is possible to establish an effective symbiosis under saline conditions, provided that a salt-tolerant Rhizobium isolate with good N-2-fixing ability is used. The use of the appropriate N-fertilizer source can enhance the growth of Pisum sativum. Hence, NH4NO3 may be preferably used under non-saline and NO3- under moderately saline conditions.