Relationship between Activities of Enzymes for the Removal of 0 2* and H20 2 and Nitrogenase in Root Nodules of Phaseolus vulgaris L

Bernhard Epping, Alexander P. Hansen and Peter Martin Institut für Pflanzenernährung (330), Fruwirthstr. 20, Universität Hohenheim, 70593 Stuttgart, Bundesrepublik Deutschland Z. Naturforsch. 50 c, 543-551 (1995); received March 15/May 2, 1995 Oxygen Derivates, Phaseolus vulgaris L.. Rhizobium leguminosarum, Rhizobium tropici, Symbiotic Effectivity Nodules of Rhizobium leguminosarum bv. phaseoli in symbiosis with Phaseolus vulgaris were compared with regard to their nitrogenase activity and activities of enzymes involved in the removal of 0 2*~ and H20 2 as well as total ascorbate content. Activities of catalase (EC 1.11.1.6), ascorbate peroxidase (EC 1.11.1.11), and total ascorbate content were consist­ ently higher in nodules inhabited by bacterial strains with higher nitrogenase activity. Values for superoxide dismutase (EC 1.15.11), and guaiacol peroxidase activity did not differ for the bacterial strains compared. On the other hand, when different plant cultivars were inoculated with the same bacterial strain, high nitrogenase activity did not correlate with a higher activ­ ity of the oxygen scavenging enzyms or a higher content of total ascorbate. In this case, values for guaiacol peroxidase activity were greatly enhanced in nodules with lower nitrogen­ ase activity. This may be part of a hypersensitive reaction of the plant cultivar against the bacterial symbiotic partner. Inhibition of catalase activity in the nodules by addition of triazole to the nutrient solution did not alter nitrogenase activity within the first nine hours after addition. It can be concluded that the activity of catalase, ascorbate peroxidase, and superoxide dismutase is not generally coupled to nitrogenase activity in root nodules of P. vulgaris.