木麻黄对土壤重金属的生长响应及积累特征

Heavy metal tolerance,accumulation and distribution in five clones of Casuarina equisetifolia

为了考察沿海防护林重要树种木麻黄对土壤重金属的耐性及修复潜力,比较了5个较耐寒木麻黄无性系(S-13、S-44、S-48、S-60和S-80)1年生扦插苗在重金属Cu、Cd、Pb和Mn复合污染土壤中的生长表现、重金属积累和分配特征。土壤重金属设置为对照组(CK)、低浓度组(T1)、中浓度组(T2)和高浓度组(T3)等4个水平。结果表明:5个木麻黄无性系在不同处理组均维持了正常生长,不同无性系的表现有差异,与CK相比,T1、T2和T3显著促进了木麻黄无性系S-13、S-44的生长,但对S-48、S-60和S-80的生长无显著影响;T3显著抑制了S-13和S-44根瘤数,而对S80则无显著影响,说明5个木麻黄无性系对重金属复合污染表现出较高耐性;木麻黄对重金属的吸收量随着土壤重金属浓度升高而增大;木麻黄对重金属的分配因重金属种类而不同,如Mn的含量为叶状小枝(小枝)>茎>根,各处理的转运系数均大于1,表明木麻黄具有较强的Mn转运能力,能把较多Mn从根部转运到地上部,地上部的Mn超过总积累量86%;Cu、Cd和Pb的含量为根>茎>小枝,表明木麻黄能把较多的Cu、Cd和Pb固定在根部,但地上部的重金属积累量超过了总积累量的50%;T3处理下,5个木麻黄无性系的重金属综合生物富集指数(CBCI)无明显差异,表明5个木麻黄无性系对重金属积累能力接近;综合生物量和CBCI表现,木麻黄无性系S-13和S-44对污染土壤具有较强的重金属修复能力;木麻黄对重金属Cu、Cd、Pb和Mn具有较强的耐性和较为突出的积累能力,对于重金属污染土壤尤其是Mn污染土壤的植物修复具有较大应用潜力。

To compare the phytoremediation potential of Casuarina equisetifolia cultivated in an artificially contaminated soil with copper( Cu),cadmium( Cd),lead( Pb) and manganese( Mn),we evaluated the tolerance of heavy metals( HMs) and accumulation capacity of oneyear-old cutting seedlings of five clones( S-13,S-44,S-48,S-60 and S-80) of C. equisetifolia.There were four HMs levels( CK,low( T1),medium( T2) and high( T3)) in this experiment.The plant growth,HMs accumulation and distribution characteristics were measured. The results showed that all clones could survive on the polluted substrate and maintain the normal growth.The five clones showed different tolerance levels to the HMs treatments. Compared to CK,HMs treatments significantly promoted the growth of S-13 and S-44. The growth of S-48,S-60 and S-80 showed no significant difference in the HMs treatments compared to CK. The HMs concentrations in tissues were increased with increasing HMs concentrations in soil. Furthermore,the HMs concentrations in tissues showed variation depending on metal speciation. For example,the concentrations of Mn in tissues were in the order of twig > stem > root. Moreover,the translocation factor( TF) values of Mn were greater than 1 in all clones and HMs treatments. The amounts of Mn in aboveground part of C. equisetifolia account for 86%,suggesting that C. equisetifolia had the higher Mn transfer capability. The concentrations of Cu,Cd and Pb in the roots were higher than in the stems and twigs. The amounts of HMs in the aboveground part were more than 50% of the total accumulation. Under the T3 treatment with the highest HMs concentration,there was no significant difference in comprehensive bio-concentration index( CBCI) of heavy metals among the five clones,indicating that they had similar accumulation capacity to heavy metals. According to the biomass and CBCI,clones S-13 and S-44 had a greater potential in phytoremediation. Taken together,C. equisetifolia had high tolerance,good accumulation and translocation capabilities for Cu,Cd and Mn. Therefore,C. equisetifolia could be a promising species for phytoremediation application on HMs pollution soil,especially for Mn pollution.