ABSTRACT
The mechanisms controlling loading and transport of amino acids and sucrose were compared in soybeans. After steady-state labeling with CO2 for two hours, about 70 percent of the recovered in the fed source leaf was in sucrose and about 15 percent was recovered in amino acids. Analysis of sap bleeding from cut stems has been used to study the transport of nitrogen in the xylem of soybean plants grown in both the greenhouse and the field. Predominate forms of nitrogen transported in xylem sap vary depending on the source of nitrogen supplied to the plants. Several experimental approaches have established a close coupling between photosynthesis (PS) and nitrogen fixation (NF) in soybeans. Although carbohydrates constitute the obvious linkage between PS and NF, little information is available on the distribution and metabolism of carbohydrates in nodules. There is often no apparent relationship between total non-structural carbohydrate content of nodules and NF.
