Vitamin B₁₂ Analogues in Non-legume Root Nodules

Abstract

IT has been shown^1–4 that cobalt must be available for legume nodules to supply fixed nitrogen efficiently to the plant bearing them. It has also been shown that in such nodules cobalt is elaborated into the form of vitamin B₁₂ analogues. Thus Levin et al.⁵, using Ochromonas and Euglena assays, reported that appreciable (though not actually stated) amounts of the vitamin were present in nodules of lucerne, clover and pea, very much smaller quantities being detected in the roots of the same plants. Shaukat-Ahmed and Evans⁶ reported that Ochromonas assay of nodules from soya bean plants supplied intermittently with 0.05 p.p.m. of cobalt indicated the presence of 519 mµg vitamin B₁₂ per g of fresh nodules. By enzymatic assay, Kliewer and Evans⁷ found appreciable amounts of vitamin B₁₂ co-enzyme(s) in the nodules of various legumes grown in the presence of the above level of cobalt.