[Response of Maize to Lead Stress and Relevant Chemical Forms of Lead]

A sand-culture experiment was carried out to research the differences in lead (Pb) chemical-form among different maize varieties for roots and shoots under Pb stress, and further investigate into the mechanism of maize endurance to resist Pb. The results showed that the wheat varieties of Zhengdan 958 and Longping 206 have the maximum Pb tolerance, whereas Lianchuang 5's tolerance of Pb was the minimum. Pb form in roots and shoots were mainly harmfulness HAc-extractable and HCl-extractable, accounting for a high proportion of 60% - 87%. Moreover, these values in roots were slightly higher than those in shoots. And concentrations of alcohol-extractable and water-extractable Pb accounted for the proportion of 6% - 20%. Under 100 mg x L(-1) Pb stress, the alcohol-extractable together with water-extractable Pb content in shoots of Longping 206 was the lowest (0.52 mg x kg(-1)), and that of in Zhengdan 958 shoots was 0.93 mg x kg(-1) which was also very low. However, for Lianchuang 5, the content could reach 2.78 mg x kg(-1). Under the stress of 800 mg x L(-1) Pb, content of alcohol-extractable together with water-extractable Pb in Zhengdan 958 shoots was 2.41 mg x kg(-1), which was still the lowest. These were probable reasons why Zhengdan 958 was more resistant to Pb stress than other varieties. Tolerance of Zhengdan 958 to Pb stress was related to it's strong ability to convert toxic Pb into non-toxic Pb.