三叶鬼针草等7种常见菊科杂草植物对重金属的超富集特征

Hyperaccumulative Characteristics of 7 Widely Distributing Weed Species in Composite Family Especially Bidens pilosa to Heavy Metals

超富集植物是植物修复重金属污染土壤技术最主要的内容,而超富集植物的筛选是植物修复技术的难点和重点.采用室外盆栽试验的方法,研究了我国北方较常见的7种菊科植物对重金属的超富集特征.盆栽筛选试验表明,蒲公英和三叶鬼针草对Cd单一及Cd-Pb-Cu-Zn复合污染的耐性较强,植物地上部镉含量分别高于其根部镉含量,地上部镉的富集系数也均大于1,具备了镉超富集植物的基本特征.以这2种植物为试材的盆栽浓度梯度试验表明,当土壤中Cd投加浓度分别为25、50、100mg·kg-1时,三叶鬼针草地上部生物量没有明显下降(p<0.05),Cd含量均大于其根部Cd含量,且其叶中Cd含量均大于100mg·kg-1,达到了Cd超富集植物应达到的临界含量标准.而蒲公英在这3个处理条件下,其叶片中Cd含量均没有超过100mg·kg-1.可见只有三叶鬼针草完全具有镉超富集植物的基本特征,是镉超富集植物.

Hyperaceumulator is the main point of phytoremediating contaminated softs by heavy metals, and the identification of hyperaccumulator is still the difficult and key step of phytoremediation. The outdoor pot-culture experiment was used to study the hyperaecumulative characteristics of 7 widely distributing weed species in Northeast of China to heavy metals. The results in screening experiment showed that Taraxacum mongolicum and Bidens pilosa indicated strong tolerance to Cd single and Cd-Pb-Cu-Zn combined pollution, their Cd concentration in shoot were higher than that in roots, and the Cd enhancement factors （ratio of heavy metal concentration in shoot to that in soil） in shoots were greater than 1 too, which displayed that the two plants were with Cd hyperaccumulative characteristics. In concentration gradient experiment, Cd concentration in leaves of B. pilosa were all greater than 100 mg·kg^-1 the minimum of Cdhyperaccumulator should have under the conditions of 25, 50, 100 mg·kg^-1 Cd added. Meanwhile, the shoot biomass of B. pilosa did not reduce significantly （p 〈 0.05）, Cd concentration in its shoots were higher than those in roots. But for T. mongolicum, Cd concentration in its shoots were not greater than 100 mg·kg^-1 in any treatment. Thus, only B. oilosa can be regarded as Cd-hyperaccumulator.