Effect of Cadmium and/or Removal of Kernels or Shoots on the Levels of Cysteine, y-Glutamyl-cysteine, Glutathione, and TCA-soluble Thiols in Maize Seedlings

Six day old maize seedlings (Zea mays L.) were exposed as intact plants (A), after the removal of kernels (B) or shoots (C) or after the removal of kernels and transfer into the dark (D) to 0 or 50 micromolar cadmium for 2 days. The roots were analyzed for fresh weight, total TCA-soluble thiols (including phytochelatins), glutathione, and its precursor compounds cysteine and gamma-glutamyl-cysteine. With all treatments, cadmium caused an increase in the contents of cysteine, gamma-glutamyl-cysteine and total TCA-soluble thiols and a decrease in glutathione content. Our data indicate that the roots are at least in part autonomous to provide the thiols required for phytochelatin synthesis.