[Objective] In order to ascertain the physiological mechanism of Si-alleviated Pb toxicity in the Salix viminalis and provide theoretical basis for the Si treatment in heavy metals contaminated soil,it was analyzed the effect of Si on Pb distribution and transport under Pb stress,membrane lipid peroxidation and osmoregulation response to Pb stress in the S.viminalis.[Method] With the disposal method of applying Si after Pb stress,Pb concentration was set two levels including 0,1.8 mmol· L-1;Si concentration was set three levels including 0,1.5,5.0 mmol· L-1 It had four blocks and each block was set six treatments.A sand culture experiment was conducted to study the regulation and control effect of Si on growth,Pb distribution and transport,membrane lipid peroxidation and osmoregulation of S.viminalis under Pb stress.[Result] Pb stress could significantly decrease the relative height and ground diameter growth rate,increase the relative electrical conductivity,O2--producing rate,MDA content,pro and sp contents of the S.viminalis leaf and root.Compared with Pb treatment,by using 1.5 mmol· L-1 Si after Pb stress,Si reduced the relative electrical conductivity,leaf 02-producing rate,MDA content and the pro content of the S.viminalis root,increased the relative height and ground diameter growth rate.Simultaneously,Si significantly reduced the content by 90.92％ on the ground of the S.viminalis,which increased the Pb content by 63.93％ in the root of it,and the total Pb content by 43.36％ in the S.viminalis.Using 5.0 mmol· L-1 Si after Pb stress,it had no significant influence to relieve Pb stress.On the one hand,Si concentration might be too high;on the other hand,it might be that the adsorption of mineral elements and buffering capacity in sand are less than in soil.[Conclusion] By analyzing several aspects of growth index,membrane lipid peroxidation and the Pb distribution and transport for Si regulation under Pb stress in the S.viminalis,it showed that Pb inhibited the growth and caused membrane lipid peroxidation of the S.viminalis.Si alleviated Pb toxicity by reducing membrane lipid peroxidation and decreasing Pb transfer from the root to the shoot of the S.viminalis.Besides,that Si improved the total Pb in the S.viminalis and inhibited Pb release to the outside.These characteristics provided theoretical basis for the Si treatment in heavy metals contaminated soil.This study is a sand culture experiment,the adsorption and diffusion barrier effects in gravel are different from that in soil.So,Si concentration,whose reaction in different plants and soil conditions is different.Therefore,it needs further research and practice in the Si treatment of heavy metal contaminated soil.%[目的]研究铅(Pb)胁迫下硅(Si)对蒿柳生长及体内Pb分布和转运的影响,分析Si在蒿柳膜脂过氧化和渗透调节响应Pb胁迫中的作用,揭示Si缓解蒿柳Pb胁迫的生理机制,为Si在重金属污染土壤的治理方面提供理论依据.[方法]采用砂培法,对蒿柳先Pb胁迫后用Si处理,其中,Pb浓度设置为0和1.8 mmol·L-12个水平,Si浓度设置为0、1.5和5.0 mmol·L-13个水平,每个区组设6个处理,共4个区组,研究Pb胁迫下Si对蒿柳生长及体内Pb分配和转运、膜脂过氧化及渗透调节指标的调控作用.[结果]Pb显著降低蒿柳株高和地径相对生长率,增大叶、根相对电导率、O2-产生速率、MDA含量、Pro和SP含量;与Pb处理相比,Pb胁迫后施用1.5 mmol·L-1Si可降低蒿柳相对电导率、叶O2-产生速率、根MDA含量和Pro含量,增大蒿柳株高和地径相对生长率;同时,Si使蒿柳地上部Pb含量显著降低90.92％,根Pb含量增加63.93％,蒿柳体内总Pb含量增大43.36％.而Pb胁迫后施用5.0 mmol· L-1Si延缓蒿柳受Pb胁迫的程度不显著,一方面可能由于Si浓度较高引起,另一方面也可能由于砂培对矿质元素的吸附和缓冲能力弱于土壤所致.[结论]Pb胁迫可抑制蒿柳生长,造成蒿柳膜脂过氧化;Si缓解Pb毒害的主要原因为Si可降低蒿柳体内的膜脂过氧化,减少Pb从根向地上部转移;同时,Si可提高蒿柳体内的总Pb量,抑制Pb向蒿柳体外排放.
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