Dinitrogen fixation and nitrogen release from roots of soybean cultivar bragg and its mutants Nts1116 and Nts1007

Abstract

Abstract Dry matter production, dinitrogen fixation activity (ARA), and the release of nitrogenous compounds from the roots of soybean (Glycine max (L.) Merr.) cv. Bragg, ntslll6 and nts1007 were studied under nitrogen-free culture conditions, Plants were sampled at the vegetative (54 d after sowing, DAS) and flowering (88 DAS) stages. Nts1116 accumulated the largest and nts1007 the smallest amount of dry matter at both sampling times. Nodule number in nts1007 which was the largest was significantly different from that of nts1116 and Bragg. Dinitrogen fixation was greater at the flowering stage and was higher in the mutants than in Bragg. Except for Bragg leaf at the flowering stage, N and ureide concentrations in the nts1007 plant parts, were higher than those of nts1116 and Bragg. Nts1116 and nts1007 accumulated the largest amount of N at the vegetative and flowering stages, respectively. The release of nitrogenous compounds from the roots of all the genotypes was higher at the flowering stage. Nts1116 and Bragg released the largest amount of nitrogenous compounds at the vegetative and flowering stages, respectively. The amount of nitrogenous compounds released that was expressed as a percentage of the amount of total N fixed was largest in Bragg and smallest in nts1007. There was a highly positive correlation between the amount of released nitrogenous compounds and the root size (r = 0.93**). Key Words: dinitrogen fixationN releasenodulessoybean mutantssuper-nodulating