PHYTOCHELATINS AS BIOMARKERS FOR HEAVY-METAL TOXICITY IN MAIZE - SINGLE METAL EFFECTS OF COPPER AND CADMIUM

Contamination of soils with heavy metals becomes more and more a probl em in many countries all over the world. In areas where metal contamin ated soils are used for food crop production, metals relatively mobile within the plant, such as cadmium (Cd) and zinc (Zn) can easily come into the food chain with great risks for human health. Since bioavaila bility of heavy metals in soils varies with soil and plant characteris tics, e.g., mineralogical and organic matter properties of the soil an d plant metal susceptibility, prediction of heavy metal uptake by plan ts by the common soil and plant chemical analysis techniques is often unreliable. Recently, the use of biomarkers has been suggested to be a suitable technique complementing chemical soil analysis. Therefore, t he usefulness of the biomarker phytochelatin (PC), a non-protein thiol , specifically induced in plants suffering from heavy metal stress, wa s tested. Maize(Zea mays L.) plants were exposed to excess copper (Cu) or Cd in nutrient solution systems and metal and PC concentrations we re monitored in plant shoot and root. Results clearly illustrated that very soon after plant exposure to the metal, PC induction started, es pecially in plant roots. Phytochelatin seems to be a useful early warn ing system for heavy metal stress in plants.