Glutamine Synthesis & Translocation in Pine

Several workers have studied translocation forms of nitrogen in the xylem sap of trees. It is generally assumed that the nitrogen compounds found in the sap are synthesized in the roots and serve as forms in which nitrogen moves to the tops of trees. Various organic compounds (e.g., amino acids, ureides) usually represent most of the nitrogen in the sap, with inorganic forms (e.g., nitrate, ammonia) being present in minor proportions (4, 5, 6, 11, 13). I have found that glutamine was the major nitrogenous constituent of the saps of seven species of pines, accounting for about 80 % of the total amino acid nitrogen at collection time in July (unpublished data). However, since Bollard's work (5) with apple trees showed considerable seasonal variation in the nitrogen content of the sap, my previous analyses of Pinus saps at one time of the year could not be considered as representative of the composition of the sap at other seasons. Bollard found that the peak concentration of nitrogen in apple xylem sap occurred at the time of blossoming. The research reported in the present paper had two main objectives: A, to follow the seasonal variation in free amino acids in the xylem sap of loblolly pine (Pinus taeda, L.), especially in relation to time of flowering; and B, to conduct preliminary studies of glutamine synthesis and translocation in pine roots and seedlings.