IAA metabolism during development of symbiosis between Phaseolus vulgaris and Rhizobium phaseoli

The time-course of peroxidase activity, IAA decarboxylation activity in viv o, and IAA content in roots and nodules of kidney bean (Phaseolus vulgaris L.) during the development of nitrogen-fixing relations was studied. A cons iderable increase in the free IAA content in the roots of plants inoculated with Rhizobium phaseoli 2626 preceded the emergence of root nodules. Auxin content in fully developed nodules and in root tissues of noninoculated pl ants was the same, whereas peroxidase activity found in nodules was higher than that observed in the root tissues of noninoculated plants. Peroxidase activity in the root tissues of inoculated young seedlings was twice as hig h as that in the root tissues of noninoculated seedlings. Peroxidase activi ty found in nodules was two times higher than that determined in the roots of the same plants. Activity of 1-C-14-IAA decarboxylation in the roots of inoculated plants exceeded that found in the roots of noninoculated plants by a factor of 1.5. The role of IAA metabolism at the early stages of devel opment of symbiotic relations between a leguminous plant and the appropriat e symbiotic bacteria is discussed.