Implications of arsenic exposure for the soybean-Bradyrhizobium symbiosis

摘要

Little is known about the effects of As exposure on the legume-rhizobium symbiosis, and thus, on the potential for N-fixation in As contaminated ecosystems. A solution culture experiment was conducted to test the effects of As on the Clycine max (soybean)-Bradyrhizobium japonicum symbiosis. Increasing As in the solution increased the time to production of the first nodule (P<0.01) and decreased the number of nodules per plant (P=0.007), probably due to a decrease in root hairs reducing infection sites for B. japonicum. However, biomass was greater in inoculated, compared to uninoculated, plants even at high As concentrations, where nodulation was minimal (P<0.05) and tissue N (P=0.082) and As (P> 0.100) concentrations were not significantly affected by inoculation status. It is suggested that future research investigate the potential of free-living B. japonicum to mitigate the negative effects of excess As on the biomass production of plants.