title: Effects of some salts and sodicity on the growth of a Rhizobium leguminosarum bv. viceae strain isolated from a salt-affected soil.
abstract: The effects of sodium (Na+), calcium (Ca2+), magnesium (Mg2+), and boron (B) concentrations and sodicity, as measured by the sodium adsorption ratio (SAR), on the growth of a Rhizobium leguminosarum bv. viceae strain isolated from a salt-affected soil were studied. The rate of growth was measured in a yeast extract-mannitol broth, amended with salts having electrical conductivity (EC) of 4, 8, and 16 dS x m(-1). Each salinity level was prepared to achieve SAR values of 10, 20, and 30 with or without graded B concentrations of 0.5, 1, 3, and 5 mg x L(-1). We found that salinity levels equal to or more than 8 dS x m(-1) had negative effects on Rhizobium growth during the first days of incubation, but the effects became less pronounced after 1 week. Na+ concentrations of more than 1.1 g x L(-1) retarded growth, especially at high SAR values (i.e., at low Ca2+ concentrations). The retardation of growth increased with increases in EC up to 16 dS x m(-1), at all sodicity levels. Mg2+ added together with Na+ or with Ca2+ + Na+ affected growth more negatively than Ca2+ + Na+ alone. The effect of Mg2+ became more pronounced with increased salinities and sodicities. It was concluded that EC of more than 4 dS x m(-1) retarded growth of Rhizobium, but only at high sodicity levels. The relative specific ion effect on growth was in the order Na+ < Ca2+ < Mg2+. The harmful effect of Mg2+ on this strain was accentuated by adding Ca2+ to the cultural medium. When SAR increased from 10 to 30, Na+ had no clear effect on growth, irrespective of the accompanied cations, i.e, Ca2+, Mg2+, or Ca2+ + Mg2+. Growth was reduced by B concentrations as low as 0.5 mg x L(-1), and the B effect was enhanced by increased salinity.
authors.affiliation: Department of Soil and Water, Omar Al-Mukhtar University, Elbeida, Libya. Mikaeel.Faituri@sml.slu.se
authors.forename: M Y
authors.initials: MY
authors.lastname: Faituri
authors.forename: Y E
authors.initials: YE
authors.lastname: El-Mahi
authors.forename: G A
authors.initials: GA
authors.lastname: El-Hassan
mesh_terms: D001895:Boron / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D007287:Inorganic Chemicals / Q000494:pharmacology*; D008274:Magnesium / Q000494:pharmacology; D016961:Rhizobium leguminosarum / Q000187:drug effects / Q000254:growth & development*; D012964:Sodium / Q000494:pharmacology*; D012988:Soil Microbiology
chemical_list: D007287:Inorganic Chemicals; D012964:Sodium; D008274:Magnesium; D001895:Boron; D002118:Calcium