Nitrogenous and carbohydrate compounds in the xylem sap of Ulmaceae species varying in resistance to Dutch elm disease

Abstract

Proline and γ-amino-n-butyric acid were present in considerable amounts in the sap of resistant species of the Ulmaceae such as Ulmus pumila, Hemiptelea davidii, and Celtis occidentalis, but occurred only in trace amounts in the sap of susceptible U. americana, U. japonica, and U. carpinifolia. The xylem sap of U. japonica, C. occidentalis, and H. davidii contained large amounts of alanine. Total concentrations of amino acids and ammonia were higher in resistant species than in susceptible species. Fructose, glucose, and sucrose were present in the sap of all the six species. Sucrose was the main sugar in the sap of U. japonica, U. pumila, and C. occidentalis; in U. americana and U. carpinifolia sucrose and fructose were present in about equal amounts; in H. davidii fructose was the major sugar.