Catalase activity and nitrogen fixation in legume root nodules

Effective white clover and soybean nodules contained more catalase than ineffective nodules. The catalase activity of a Rhizobium japonicum strain collected from effective soybean nodules was greater than that in a strain from the ineffective root structures. Ineffective Rhizobium trifolii mutants grown in laboratory media had less catalase than their effective parent strains, but no relationship between catalase content and effectiveness was noted among laboratory-grown R. japonicum cultures. Effective nodules from soybean but not from white clover were somewhat richer in peroxidase than the analogous non-nitrogen-fixing root structures. No correlation was evident between effectiveness and phenol-oxidase activity of soybean nodules.