Abstract: With hydroponics and polyacrylamide gel electrophoresis (PAGE),this paper studied the effects of lead stress on the activities of peroxidase (POD),superoxide dismutase (SOD) and catalase (CAT),and their isoenzymic band numbers in cucumber seedlings.The results showed that the isoenzymic bands and expression quantity of POD decreased gradually with increasing lead concentration.The SOD activity increased with increasing lead concentration within the range of 0～500 mg Pb·L^-1,reached the maximum at 7th day,and then decreased rapidly,being lower than the control of the same period.Under the concentration of 900 mg Pb·L^-1,the SOD activity decreased with time.The isoenzymic bands and expression quantity of SOD were negatively related to lead concentration.No significant change was observed in the isoenzymic bands of CAT,but a significant difference was found in the expression quantity of CAT isoenzymes.

Key words: Molecular markers, Plant population, AFLP, RAPD, RFLP, SSR