The activities of three enzymes and the concentration of intermediates involved in the synthesis of N,N-dimethyltryptamine (DMT) from endogenous tryptophan (TRP) have been measured in vitro in seedlings of Phalaris aquatica L. cv Australian Commercial over 16 days after planting. The activities of tryptophan decarboxylase and the two N-methyl-transferases increased rapidly to maximal rates of...