The physiological significance of the leaf nodules of psychotria

Abstract

In 6-month growth experiments it was found that leaf-nodulatedPsychotria mucronata seedlings grown in N-poor soil showed a restricted growth and developed severe nitrogen-deficiency symptoms in the leaves. Plants in the same soil supplied with NO3-N showed healthy growth and dark green leaves. Detached Psychotria leaves bearing leaf nodules exposed to an atmosphere containing N15-labelled nitrogen gas or acetylene gas gave no evidence of nitrogen fixation, either in the light or in the dark or in both in succession. Therefore nitrogen fixation is probably not associated with the leaf nodules.