Nitrogen Fixation by the Leaf-nodule Endophyte of Psychotria bacteriophila

INVESTIGATIONS of the symbioses in root-nodules of legumes and non-legumes have established that nitrogen fixation occurs in the nodular tissue 1 . Although some reports have appeared describing the leaf-nodule symbiosis in Psychotria 2–4 no isolate of the endophyte is at present available, and it has not been unequivocally established that nitrogen fixation is involved. We now report that the isolated endophyte fixes atmospheric nitrogen in pure culture and, apparently, in the plant as well. It is known that plants either naturally or experimentally freed of the endophyte are dwarfs 2,3 . Nitrogen fixation does not fully account for these observed effects.