Rhizobial production of vitamin B12 active substances and their localization in some leguminous plants
1998
Yoshida, S. (Nagoya Univ. (Japan). Faculty of Agriculture)
The purposes of this investigation are to clarify the production of vitamin B12 active substances by rhizobia and to examine their localization in the plant parts of some legumes as related to their nodulation by the Euglena bioassay method. The results obtained are as follows: 1) All of the rhizobia tested had the ability to produce B12 active substances. However, no significant correlation existed among the species of rhizobia. 2) The production of active substances markedly increased with the increase of cobalt concentration in the culture medium. The Rhizobium meliloti and Bradyrhizobium japonicum tested in this experiment required more than 1 mg L(-1) of cobalt chloride for the maximum production of B12 active substances. The application of nitrate to rhizobial culture medium slightly enhanced the production of B12 active substances. 3) The larger part of B12 activity in the culture media of R. meliloti and B. japonicum was found to depend on cobalamin by paper chromatography. 4) A higher concentration of B12 active substances was detected in the bleeding sap of nodulated kidney bean as compared to the non-nodulated one. 5) The concentration of B12 active substances was higher in the underground part than in the aerial part, and the tendency was more clearly observed in nodulated lupin plants than in non-nodulated lupin plants. 6) The greater part of B12 active substances in nodulated plants was present in the nodules of the leguminous species tested in this experiment. The concentration in the nodules was about 10 to 60 times higher than that in the root and about 100 to 700 times higher than that in the aerial parts. However, the concentration in soybean nodules fluctuated largely with the age of the plant
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