The Influence of Nitrogen Nutrition on the Accumulation of Free Amino Acids in Root Tissue ofUrtica dioicaand their Apical Transport in Xylem Sap

摘要

Urtica dioicaplants were grown on a nitrogen supply of 3, 15 and 22 mM with nitrate and ammonium as nitrogen source. In contrast to nitrate reductions amino acid synthesis occurred in root tissue. At 3 mM ammonium obviously the amino acids were rather transported via xylem upwards to the shoots than stored in the roots. Particularly increased ammonium supply led to stimulated storage of free amino acids in the roots, mainly as asparagine and arginine. In xylem asparagine was the dominant nitrogen transporting compound, while arginine was hardly translocated. With the enhancement of nitrogen supply, the second amide, glutamine, became more and more important with respect to the transport of nitrogen.