Abstract:The extracts from leaves of nodulated soybean (Glycine max (L.) Merr. ) cv. Bragg and its nodulated mutants i. e. non-nodulated Nod 49, supernodulated nts 382 and nts 246 contained inhibitors of activities iNR, c1NR and c2NR in vitro. Both white light illumination of 300 μE · m-2 · s-1 and inoculation with strain USDAll0 were essential conditions for ac- cumulating these inhibitors in leaves. Comparing inhibiting activities of the extracts from different varieties indicated that Nod 49 extract showed stronger inhibition than Bragg extract did, but nts 382 extract had only weakest inhibitory effect. The inoculated Bragg root extract possessed the same inhibitory activity as its leaf extract. The inoculated nts 382 root extract, like its leaf extract, showed only a little inhibitory activity. However inoculated Nod 49 root extract lead to an inhibition of leaf c2NR activity, which was different from its leaf extract that inhibited three kinds of NR activities. The above results suggested that both leaf and root extracts contained common inhibitory factor which was accumulated after inoculation.