Organic Nitrogen Compounds in Tree Xylem Sap

The free amino acids and ureides occurring in the xylem saps of 60 species of trees growing in the vicinity of Durham, N. C., were determined. The main compound found in saps of the seven species of the genus Pinus was glutamine. This amino acid represented 73 to 88 percent of the total organic nitrogen accounted for. A survey of 53 other species that represented 42 genera in 28 families of conifers and hardwoods showed that seven compounds were of major importance in one or more species. These compounds were allantoic acid, arginine, asparagine, aspartic acid, citrulline, glutamic acid, and glutamine. There was a tendency for the species in a given family to contain the same compounds as major constituents of the saps. The results of the study are discussed briefly in regard to possible implications for research in tree nutrition.