Metal speciation in xylem exudate of Lycopersicon esculentum Mill-technetium

This paper deals with a new analytical approach for studying metal speciation in the xylem, as applied to the nuclear waste metal technetium (⁹⁹Tc) in tomato plants (Lycopersicon esculentum Mill, cv. Tiny Tim). Special attention was paid to sampling protocols and sample handling so that metal oxidation/reduction processes during analytical procedures did not influence the results. Marker Tc-ligand complexes were synthesized in vitro (Tc-cysteine, Tc-histidine, Tc-citrate, and Tc-nicotianamine) and sampling was performed under both argon and atmospheric conditions. Analyses were carried out using paper chromatography, gel electrophoresis (PAGE), and reversed phase ion-pair chromatography (RP-IPC). The results show Tc to be present predominantly in the TcO₄⁻ form in the xylem, indicating transport similarities with molybdenum and chromium. Probably, the approach used is also valuable in other metal-speciation studies in the xylem.