Comparative distribution and metabolism of Xylem-borne amino compounds and sucrose in shoots of Populus deltoides

• Published in: Plant physiology (Bethesda) Vol. 77; no. 2; pp. 418 - 428
• Main Authors: Vogelmann, T.C, Dickson, R.E, Larson, P.R
• Format: Journal Article
• Language: English
• Published: Rockville, MD American Society of Plant Physiologists 01.02.1985
• Subjects: Absorption. Translocation of ions and substances. Permeability; Agronomy. Soil science and plant productions; Amino acids; AMINO COMPOUNDS; Biological and medical sciences; COMPOSE AMINE; COMPUESTOS DE AMINA; Economic plant physiology; Fundamental and applied biological sciences. Psychology; Internodes; Leaves; METABOLISM; Metabolism. Physicochemical requirements; METABOLISME; METABOLISMO; Nutrition. Photosynthesis. Respiration. Metabolism; Organic acids; Parenchyma; Phloem; Plant physiology and development; Plants; POPULUS DELTOIDES; Radiocarbon; STEMS; SUCROSA; SUCROSE; TALLO; TIGE; TRANSPORT; TRANSPORTE; XILEMA; XYLEM; XYLEME; Translocation; Populus deltoides; Sucrose; Dicotyledones; Aminoacid; Angiospermae; Spermatophyta; Conductive tissue; Salicaceae
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.77.2.418

The transport and metabolism of xylem-borne amino compounds and sucrose were investigated in rapidly growing shoots of cottonwood (Populus deltoides Bartr. ex Marsh.). 14C-labeled glutamine, threonine, alanine, glutamic acid, aspartic acid, and sucrose were applied to the base of severed stems for transport in xylem. Distribution and metabolism of the compounds were followed with autoradiography, microautoradiography, and radioassay. Three utilization patterns were observed: (a) little alanine and sucrose was transported to the laminae of either mature leaves or developing leaves. These compounds were taken up from xylem free-space and utilized in adjacent tissue; (b) threonine also did not move into mature leaves but was translocated to developing leaves or utilized in the stem; (c) glutamic acid and aspartic acid were transported directly into the laminae of mature leaves via the xylem. Relatively less 14C was retained in stems compared to the other compounds. Metabolism of the test compounds also differed considerably. 14C from amino acids moved primarily into organic acids and protein. The 14C from sucrose was widely distributed among the chemical fractions, with a high percentage found in structural carbohydrates. Clearly, cottonwood stems contain efficient uptake and transfer systems that differentiate among various compounds moving from root to shoot in xylem.