中文摘要：

为正确评价重金属污染下冬小麦根际土壤微生态系统的安全性和稳定性，采用盆栽试验法研究了铅（Pb）含量低于国家“土壤环境质量标准（GB15618—1995）”规定的Ⅱ类土壤环境基准值（350．00mg／kg，干土）时，与镉（cd）复合处理对冬小麦幼苗根际土壤氧化还原酶活性、肥力指数（Biologicalindexoffertility，BIF）及碳／氮（C／N）的影响．结果表明：（1）幼苗生长3周时，Cd处理下过氧化氢酶和多酚氧化酶活性显著（P〈0．05）增加，脱氢酶活性显著（P〈0．05）降低；碉时多酚氧化酶和过氧化氢酶活性显著（P〈0．05）降低；12周时，多酚氧化酶和脱氢酶活性显著（P〈0．05）降低．此外，根际土壤生物学肥力指标BIF值主要表现为降低，而根际土壤C／N值在幼苗生长3周和12周时显著（P〈0．05）降低，碉时却极显著（P〈0．01）升高．（2）低含量Pb与Cd对脱氢酶和过氧化氢酶活性、BIF值主要起协同抑制效应，对多酚氧化酶活性表现出拮抗效应．幼苗生长3周和12周时，低含量Pb可减轻Cd对C／N值的降低效应，7周时，低含量Pb和Cd协同促进C／N值升高．土壤Pb含量低于国家“土壤环境质量标准”规定的Ⅱ类土壤环境基准值时，仍会明显影响Cd污染下冬小麦幼苗根际土壤的生化功能特征．

英文摘要：

The aim of this research was to evaluate the stability and security of rhizosphere soil micro-ecosystem of winter wheat under the heavy metal polluted soil. The effects of low doses of Pb （350.00 mg/kg in dry soil） and Cd on soil oxidoreductase activiiies, biological index of fertility （BIF）, and the C ： N ratio in winter wheat seedling rhizosphere were investigated using the pot experiment. The results indicated that： （1） The activities of polyphenoloxidase and catalase increased significantly （P〈0.05） and that of dehydrogenase decreased significantly （P〈0.05） in Cd treatment when wheat seedlings had grown for three weeks. The activities of polyphenoloxidase and catalase decreased significantly （P〈0.05） in Cd treatment at the seventh week. In the meantime, the BIF value decreased significantly in Cd treatment at three growth stages, and the C ： N ratio increased significantly （P〈0.05） at the third and twelfth weeks and decreased significantly （P〈0.01） at the seventh week in Cd treatment. （2） The activities of catalase and dehydrogenase reduced significantly （P〈0.05） in the treatments of the low dose of Pb and Cd, and the low dose of Pb treatment alleviated the effect of Cd on polyphenoloxidase activity. Meanwhile, the low dose of Pb stimulated evidently the repression of Cd on the BIF value. And the low dose of Pb reduced the repression of Cd on the C ： N ratio at the third and twelfth weeks and the C ： N ratio increased in Pb/Cd treatment compared with Cd treatment alone at the seventh week. （3） The low dose of Pb still significantly （P〈0.05） affected the biochemical function of Cd polluted soil in winter wheat seedling rhizosphere.