Symbiotic effectiveness, rate of respiration and glutamine synthetase activity of sodium azide resistant strains of Rhizobium leguminosarum biovar trifolii

Nitrogen fixing efficiency of sodium azide-resistant strains of Rhizobium l eguminosarum by. trifolii was studied in symbiosis with berseem clover plan ts in chillum jars. Rate of respiration and glutamine synthetase activity w ere tested in cultured cells and nodules, respectively. It was observed tha t shoot dry weight and percentage shoot nitrogen were maximum in plants ino culated with strains resistant to 15 mu g ml(-1) sodium azide. Rate of resp iration in cultured cells was lowest in strains resistant to 15 mu g ml(-1) sodium azide and highest in strains resistant to 5 mu g ml(-1) sodium azid e. A negative correlation was observed between rate of respiration (in cult ured cells) and shoot dry weight of host plants. Glutamine synthetase activ ity was maximum in nodule extracts of host plants inoculated with strains r esistant to 5 and 10 mu g ml(-1) sodium azide, whereas it was minimum for s trains resistant to 15 mu g ml(-1) sodium azide. Hence, resistance to low d oses (15 mu g ml(-1)) of sodium azide, together with lower respiratory and glutamine synthetase activities, could be used as a potential method for is olating the symbiotically effective strains of Rh. leguminosarum bv. trifol ii.