Hydroponically grown tomato plants (Lycopersicon esculentum P. Mill. cv Golden Boy) exposed to 100 micromolar cadmium sulfate produced metal-(γEC)nG peptide complexes containing acid-labile sulfur. The properties of the complexes resemble those of the cadmium-(γEC)nG peptide complexes from Schizosaccharomyces pombe and Candida glabrata known to contain a cadmium sulfide crystallite core. The crystallite is stabilized by a sheath of peptides of general structure (γGlu-Cys)n-Gly. The cadmium-peptide complexes of tomato contained predominantly peptides of n3, n4, and n5. spectroscopic analyses indicated that the tomato cadmium-sulfide-peptide complex contained CdS crystallite core particles smaller than 2.0 nanometers in diameter.