小麦不同生育时期Cd、Cr、Pb污染监测指标体系

The pollution monitoring index system of wheat at different growth stages under the stress of Cd,Cr and Pb

以小麦为供试材料,分别采用发芽试验、溶液培养、土柱栽培等毒理试验方法,研究了小麦萌芽期、幼苗期及成株期受重金属污染毒害的指标体系。结果表明,①小麦根伸长抑制率可作为萌芽期重金属污染评价的一项生物指标;Cd、Cr、Pb对小麦根生长的7d半效应浓度(EC50)值分别为1.39、0.20mmo.lL-1和2.75mmol.L-1,据此得到3种重金属对小麦同一性状的毒性次序为Cr>Cd>Pb;此外各性状抑制率与胁迫浓度的关系可用双曲线模型y=x/(a+x/100)或指数曲线模型y=a(1-exp(-bx))较好模拟。②Cd、Cr、Pb单一污染胁迫对小麦幼苗性状的毒性次序均以影响叶面积和冠部干重为主,表明叶面积和冠部干重为幼苗期污染监测的敏感指标;重金属对除根干重外所有性状的毒性次序:Cr>Cd>Pb,该毒性次序是根据引起50%抑制的临界浓度即EC50值确定的;各性状抑制率与胁迫浓度的关系可用直线模型、或双曲线模型、或指数曲线模型较好模拟。③重金属单一污染胁迫造成小麦籽粒产量下降幅度是Cd>Cr>Pb;二元互作对产量影响的重要性次序为CdCr>CdPb>CrPb;在Cd、Cr、Pb复合污染胁迫条件下,穗数可以作为成株期重金属污染监测的首选指标。以上指标可为农田小麦重金属污染的监测和综合治理提供一些理论依据。

With wheat as test material,a series of experiments including toxic germination tests,hydroponic and soil column culture were carried out to study the pollution monitoring system of toxic heavy metals in wheat at different growth stages.EC50＇s were used to order toxicity of the heavy metals.The results indicated that：①The decrease in root elongation rate might be an effective bio-marker to estimate heavy metal pollution.The 7d EC50 of Cd,Cr and Pb on the root elongation were 1.39mmol·L^-1,0.20mmol·L^-1 and 2.75mmol·L^-1,so their toxicity ranked as Cr〉Cd〉Pb.Relations between the inhibition to each traits and heavy metals concentrations were well fitted into math models of hyperbola equation y = x/（a ＋ x/100）or exponential curve y = a（1-exp（-bx））.②Heavy metal stress to wheat seedlings was most obvious in leaf area（LA）and top weight（TW）,so LA and TW may act as sensitive indices for pollution monitoring at seedling stage.All traits except for root weight were affected by heavy metal in that order of Cr〉Cd〉Pb.Relations between inhibition rates to wheat agronomic traits and heavy metal concentrations were better showed by linear equation,hyperbola equation or exponential curve.③Toxicity of soil heavy metals in terms of grain yield decrease ranked as Cd〉Cr〉Pb.Interactions between any double stresses of heavy metals on grain yield followed as CdCr〉CdPb〉CrPb.The ear number was the first choice to be used for pollution monitoring at mature stage under multiple stresses.Our obtained results will provide theoretical basis for pollution monitoring and comprehensive control in farmland.