Foliar nitrogen and changes in free amino acid composition of Solanum lycopersicum under cadmium toxicity: kinetics of 15NH4+

Abstract

Glutamate metabolism and amino acid translocation were investigated in the control and cadmium stressed shoots of tomato (Solanum lycopersicum -63/5 F1), using ( 15 N] ammonium was incorporated into asparagine, which served as an additional detoxification molecule. In the presence both of methionine sulfoximine and cadmium, glutamate, alanine, and g-amino butyrate of leaf tissue continued to become labelled with 15 N. The labelling kinetics of amino acids in leaves of tomato plants in the presence of cadmium show that continued assimilation of [15 N] ammonium can occur when the glutamine synthetaseglutamate synthase cycle is inhibited. The data provided evidence that the glutamine synthetase pathway and glutamate dehydrogenase play distinct roles in the source-sink nitrogen cycle of tomato leaves under cadmium stress conditions.