1) Buckwheat had high phenylalanine deaminase activity, while it did not show a detectable activity of tyrase at every growing stage of its stem.2) At every growing stage shoot apex always showed highest phenylalanine deaminase activity, the internode adjacent to it lower activity and the next internode far lower activity. The part where the secondary tissues had already developed had, however, fairly high enzyme activity. Nearly 80% of total enzyme activity in the whole plant distributed in the region where the secondary tissues had already developed.3) The distribution of the phenylalanine deaminase activity in the tissues indicated that cambial tissue and adjacent tissues have the high enzyme activity.4) Comparison between primary and secondary tissues showed that a fairly good parallelity was present in their phenylalanine deaminase activity and lignin content.