Nodulation, Nodule Growth and Proton Release by Soybean Plants Cultivated in Hydroaeroponic System as Affected by Salinity and Bradyrhizobium japonicum Strains

The present study aims to investigate the nodulation and nodule growth and proton release by soybean plants, Essor, inoculated with two strains of Bradyrhizobium japonicum, G49 and USDA122, tested for their salinity tolerance. The plants were cultivated in aerated saline solutions from the germination or 21 day after transplanting. By increasing salt concentrations, the strains were slowly grown. This effect was more obvious for strain USDA122 than G49 indicating that strain USDA122 was more sensitive to salts than the other one. Salt decreases the different parameters of plant growth. However, its effect was more pronounced in plants with early exposure to saline solutions. The nodule dry weight was the most affected. Nodule number was systematically less affected by salt than nodule mass. Plants inoculated with strain, G49 seem to be more tolerant than those inoculated with USDA122, especially for plants continuously growing in the high saline solution treatment. Salinity application significantly decreased the total proton release, whatever the strain used for inoculation. However, plants inoculated with strain G49 released more protons than those inoculated with the other bacterial strain. Increasing both of salinity concentration and time of application caused an increase in the values of specific proton release.