低含量Pb2+对Cd2+污染下冬小麦幼苗根系过氧化物同工酶的影响

【目的】研究Pb²⁺含量低于国家“土壤环境质量标准(GB 15618-1995)”规定的Ⅱ类土壤环境基准值(300.0 mg/kg)时，其对Cd²⁺污染下冬小麦幼苗根系过氧化物(POD)同工酶表达的影响，为正确评价土壤重金属污染条件下冬小麦生长发育的安全性和稳定性提供科学依据。【方法】采用盆栽试验，在不同含量Cd²⁺和Pb²⁺/Cd²⁺污染条件下培育冬小麦幼苗，待幼苗生长3周、7周和12周时，采集冬小麦幼苗根系，采用聚丙烯酰胺凝胶电泳(PAGE)，分析低含量Pb²⁺对Cd²⁺污染下冬小麦幼苗根系POD同工酶的影响。【结果】在幼苗生长的3周、7周和12周3个阶段中，土壤Cd²⁺污染对冬小麦根系POD同工酶的表达表现出了抑制效应；3周龄时，冬小麦根系POD同工酶表达量受Cd²⁺抑制影响最强，随着冬小麦生长时间的延长，Cd²⁺的影响开始减弱，且在冬小麦3周和7周龄时，20.0 mg/kg Cd²⁺对冬小麦根系POD同工酶表达量的抑制作用最强。除3周龄时120.0 mg/kg Pb²⁺可减缓20.0 mg/kg Cd²⁺对冬小麦根系POD同工酶表达的抑制作用外，低含量Pb²⁺对Cd²⁺污染条件下冬小麦根系POD同工酶的表达均起协同抑制效应。【结论】冬小麦幼苗生长初期，土壤Cd²⁺污染对其根系POD同工酶表达表现出较强的抑制作用，随着冬小麦生长时间的延长，Cd²⁺的抑制作用减弱；当土壤中Pb²⁺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(300.0 mg/kg)时，其增强了Cd²⁺污染对冬小麦根系POD同工酶表达的抑制作用。

Effects of the low dose of Pb2+ on the response of isozymes of POD of winter wheat seedlings roots to Cd2+ stress

【Objective】 The effects of the low dose of Pb2+(< 300.0 mg/kg) on the response of POD isoenzyme of winter wheat seedlings roots to Cd2+ stress were analyzed to provide theoretical basis for environmental contamination.【Method】 The pot was used to culture winter wheat seedlings under stresses of Cd2+ and Pb2+/Cd2+,and the Polyacrylanid Gel Electrophoresis(PAGE) was used to analyze the expression of POD isoenzyme.【Result】 The expression content of POD isozymes of roots was inhibited by Cd2+ contamination.The inhibition of Cd2+ on the expression content of POD isozymes was the most powerful in the third week after winter wheat seedlings emerged and the influence weakened with the extension of wheat growth stage.The inhibition of 20.0 mg/kg Cd2+ on the expression content of POD isoenzymes was significant in the third and seventh week after winter wheat seedlings emerged.Low dose of Pb2+ aggravated the inhibition of Cd2+ on the expression content of POD isoenzymes of winter wheat roots except for the relief of 120.0 mg/kg Pb2+ to the inhibition of 20.0 mg/kg Cd2+ on it at the third week.【Conclusion】 Cd2+ inhibited significantly the expression content of POD isoenzymes at the first growth stages of winter wheat seedlings and the inhibition weakened with the extension of growth stage.The low dose of Pb2+(<300.0 mg/kg) aggravated significantly the inhibition of Cd2+ on the expression of POD isoenzymes of winter wheat roots.