Trace elements species fractionation in rye flour and rye (Secale cereale L.) seedlings

The fractionation of Cd, Cu, Mo, Ni, and Zn species in extracts of rye (cv. Fernando) seedlings (grown up in both standard and Cd²⁺-enriched medium) and rye flour was performed by SEC/ICP−MS method. The majority of Cu, Zn, and Ni in all samples were bound in the 1–2 kDa fraction. Molybdenum occurred in all samples in the fraction of 3 kDa. During five days of cultivation in a solution of 30 µmol/l Cd²⁺, the plants accumulated as much as 5 mg/kg fresh matter of Cd, but its soluble portion represented only 12–15%. The prevailing portion of Cd complexes was contained in the fraction of 3 kDa, while the minor part occurred in the fraction of 20 kDa. The speciation of elevated Cd in plants differs from that of other metals present at a physiological level. The metal-rich fractions of the extracts of all samples (i.e. those of 1–2 kDa) were refined by immobilised metal affinity chromatography. The isolated ligands of trace elements were peptides rich in dicarboxylic aminoacids.