Survey of the Plant Kingdom for the Ability to Bind Heavy Metals through Phytochelatins

Differentiated plants and suspension cultures of the taxonomic divisions Bryophyta, Pteridophyta, and Spermatophyta have been investigated as to their ability to detoxify heavy metals like Cd2+ through the formation o f (y-Glu —Cys)„—Giy peptides, the phytochelatins. Over 200 individual plants have been checked and there was not a single exception observed. Only in the order Fabales several species mainly o f the tribus Fabaceae form upon exposure to Cd2+ ions peptides o f the general structure (y-Glu — Cys),, —ß-Ala, the homo-phytochelatins. The existence of glutathione and homo-glutathione within a given species determines whether phytochelatins or their homo-derivatives are formed. The ability to form phytochelatins for metal homeostasis and metal detoxification is a principal feature o f plant metabolism.