不同土壤铅含量条件下三裂叶豚草生长及铅富集特征

Growth and Pb Accumulation of Ambrosia trifida L. in Soil with Different Pb Concentrations

随着道路交通的快速发展,公路两侧土壤铅含量通常显著高于土壤背景值。三裂叶豚草(Ambrosia trifida L.)是入侵我国北方地区的重要杂草,其在公路两侧通常形成单优种群呈集群分布,但关于土壤铅含量对三裂叶豚草生长发育的影响尚不清楚。采用盆栽试验,设置土壤铅含量分别为背景值(CK),100,250,500,1000mg·kg^(-1)共5个处理,分析土壤中不同的铅含量对三裂叶豚草生长及铅富集特性的影响。结果表明,随着土壤铅含量的升高,三裂叶豚草根系和地上部分的铅含量均增加,而且随着生长发育三裂叶豚草组织中铅含量不断上升。但三裂叶豚草铅转运系数低,根系铅含量要显著高于地上部分铅含量,根系富集系数高于地上部分富集系数。三裂叶豚草生物量随着土壤铅含量的增加先升高后降低。低浓度的铅促进三裂叶豚草生长、根冠比增加和叶绿素含量提高。土壤铅含量为250mg·kg^(-1)时,三裂叶豚草生物量最大。但土壤铅含量继续增加,三裂叶豚草生物量下降,叶绿素含量降低。可见,在一定浓度范围内土壤铅能够促进三裂叶豚草生长,三裂叶豚草通过将铅积累在根系中以适应土壤铅含量的增加,公路两侧高铅含量的土壤斑块将有助于三裂叶豚草的分布和扩散。

More and more amounts of Pb have been accumulating in soil around roads than unpolluted background soil since the rapid development of traffic. Ambrosia trifida L. is a northern America annual grass invading much of roadsides in northern China and forms mono-dominant clumped distribution population. However, the effects of the high Pb content soil on A. trifida with are not clear. A pot experiment was conducted to examine the effects of Pb in soil on growth and Pb accumulation of A. trifida under different Pb content （soil background value, 100 mg·kg-1, 250 mg·kg-1, 500 mg·kg-1, 1000 mg·kg-1）. Both the Pb content in aboveground and belowground of A. trifida increased with the increase of Pb concentrations of soil and the growth stage. However, the contents of Pb were significantly higher in root than aboveground. The more bioaccumulation factor and the lower biological transfer coefficient of root than aboveground also indicated the Pb in A. trifida were mainly accumulated in root. The biomass of A. trifida, ratio of root and aboveground, content of chlorophyll increased at low Pb concentration but decreased at high Pb concentration. The biomass of A. trifida was the highest in soil treatment with 250 mg ·k g -1 Pb. When the Pb concentration more than 250 mg ＊kg-1, the biomass and chlorophyll content of A. trifida decreased. Adaption of A. trifida to raised Pb content in soil by accumulating absorbed Pb in its roots and increased its growth and development in a certain concentration range of Pb in soil suggested that the increasing Pb concentration in soil would promote A . trifida population establishment and dispersal.