EFFECT OF SALINITY ON RHIZOBIUM-ROOT-HAIR INTERACTION, NODULATION AND GROWTH OF SOYBEAN

Abstract

The interaction of rhizobia with root-hairs in the rhizosphere of soybean was investigated under saline concentrations of 0–1.8%. At 1.0% NaCl, root-hairs showed little curling and deformation in response to rhizobial inoculation. At 1.5% or above, shrinkage of root-hairs was evident. The growth and multiplication of rhizobia declined rapidly when NaCl concentrations were increased from 0.2 to 0.8%. At higher concentrations, rhizobial growth was minimal. Nodulation was completely eliminated at concentrations of 1.2% NaCl or higher and increasing salinity caused a gradual continuous decline in soybean fresh weight and plant height. The failure of soybean to nodulate at high salinity was attributed to decreased rhizobial colonization and, at higher salinity, to shrinkage of root-hairs. Thus, the reduction in soybean growth under conditions of high salinity could only be partly accounted for by the reduction or failure in nodulation.