Cadmium toxicity effects on growth, mineral and chlorophyll contents, and activities of stress related enzymes in young maize plants (Zea mays L.)

摘要

Maize cv. Volga plants were grown in a nutrient solution containing increasing cadmium concentrations (0.001-25μM), under controlled growth conditions. Changes in the growth parameters and enzyme activities directly or indirectly related to the cellular free radical scavenging systems were studied in the roots and leaves of 14-day-old plants. A significant decrease in both shoot length and leaf dry weight was observed with 25μM Cd, while chlorophyll pigment concentrations in the 4th leaf decreased with concentrations of 1.7μM Cd and above. Changes in enzyme activities occurred at lower Cd concentrations in solution. Peroxidase (POD) activity increased in the 3rd and 4th leaf, but not in roots. In contrast, glucose-6-phosphate dehydrogenase, isocitrate dehydrogenase and malic enzyme activities decreased in the 3rd leaf. According to the relationship between the POD activity and the Cd content, a toxic critical value was set at 3 mg Cd/kg dry matter in the 3rd leaf and 5 mg Cd/kg dry matter in the 4th. Anionic POD was determined both in roots and leaf protein extracts. No changes in the isoperoxidase patterns were detected with Cd toxicity. It is suggested that the measurement of enzyme activities should be utilised to assess the phytotoxicityof Cd-contaminated soils on maize plants.