Effects of Nitrogen Application on Physiological Characteristics of Nitrate-Tolerant Mutants of Soybean

Abstract

Nitrate-tolerant mutants of soybean (Glycine max 〔L.〕 Merr.), nts1116 and nts1007 and their parent cultivar Bragg were grown in field. Plants were harvested at flowering, pod elongating and pod filling stages; and analyzed for nitrogenous components and sugar. The highest total N and ammonium-N concentration were found in nodules followed by leaf, stem and root. There were small differences in the concentrations between N- and non-N-applied plants. Nts1007 showed higher concentrations in almost all plant parts than Bragg and nts1116. Allantoin-N concentrations was highest in nts1007, especially in nodule. Nitrogen application brought about the remarkable decrease of allantoin-N in stem and root. Slight differences in sugar concentrations were observed between N-applied and non -N-applied plants and among three lines. The concentrations in root and nodule of nts1007 were higher than Bragg and nts1116, indicating that a heavily nodulating mutant, nts1007 was not recognized to be restricted in energy supply for nitrogen fixation as compared to Bragg or nts1116. There were small differences in the characteristics in pods between N- and non-Napplied plants of all lines except for allantoin-N and sugar of nts1007. Allantoin-N showed higher concentration in nts1007 than in other two lines at pod elongating stage. Sugar contents showed a decreasing tendency that was distinct in nts1007 applied with nitrogen. The high allantoin-N and low sugar concentrations in pod shells of nts1007 were considered to be due to higher N fixation by superabundant nodulation