To examine the influence of nodulation on the production of nitrogenous compounds, soybean plants (Glycine m a x var. Tamanishiki) were grown with or w i t h o u t N-fertilizer in the field, and the changes in amino-N and allantoin-N content in the different organs were determined throughout the growth period. I n the stem allantoin-N markedly increased after the flowering period and then decreased during seed formation. Allantoin accumulated in the pod (up to 70 per cent of total alcohol soluble-N) during pod formation, while in the seed the main N-compounds were amino acids, the allantoin coneentra~ tion being v e r y low. In well-nodulated soybeans grown w i t h o u t N-fertilizer, allantoin content in every plant organ was always high compared to beans grown with N-fertilizer, but amino-N content was comparatively low.
Another experiment, in which soybean plants were allowed to form nodules by growing on a N-free medium, and in which a fixed-N supply was then controlled by the addition of various levels of ammonium, was made in a greenhouse. \ Β₯ h e n nodules were formed, the subsequent addition of high concentrations of a m m o n i u m caused the accumulation of allantoin as well as the accumulation of amides and arginine. A possible role for allantoin and some aspects of its production in soybeans are discussed.