Cytochemical localization of peroxidase during the development of root nodules of Pisum sativum L.

Abstract

Sumamry Isoenzymes of peroxidase and IAA oxidase were separated electrophoretically from the soluble and cell-wall fractions of mature root cortex and root nodules of Pisum sativum L. It was shown that all IAA-oxidase isoenzymes exhibited peroxidase activity. In cytochemical localization studies of peroxidase in roots and root nodules the absence of activity specifically in the cytoplasm of root-nodule bacteroid cells was demonstrated. This result is interpreted to mean that hyperauxiny of root nodules may be due to low or even no IAA-oxidase activity in the bacteroid cells. In early nodulation the peroxidase activity in the infected area of the root cortex was not suppressed but had even increased. The results of preliminary experiments with isolated rhizobial auxin support the suggestion that nevertheless IAA is the auxin involved in the induction of the first cell divisions in the formation of nodules.