Pot experiments were conducted to study the effects of ethylene diamine tetraacetic acid (EDTA) and citric acid (CA) on copper accumulation and translocation inAmaranthus retroflexusL., with exogenous copper concentrations of 0, 100, 200, 400 and 800 mg·kg-1. The concentrations of Cu with different speciations in both rhizosphere and bulk soil, and its enrichment characteristics in plant tissue were determined after adding 2.5 mmol·kg-1 CA or EDTA to different copper treatment. Results showed that the ability of copper accumulation in different plant tissues followed the sequence of roots > leaves> stems when copper contents were less than 400 mg·kg-1, while roots > stems > leaves when copper contents were 400 mg·kg-1. BCFs and TFs ofA. retroflexuswere both less than 1, which indicated thatA. retroflexuswas not a copper hyperaccumulation plant under the present experiment condition. Both EDTA and CA can effectively improve enrichment ability of the plant for copper and enhance the transportation of copper from roots to shoots; EDTA was more effective, causing 3512.71 mg·kg-1 of shoots uptake under the 800 mg·kg-1 copper content condition. The contents of total copper and exchangeable speciation inrhizosphere soil were increased for the EDTA amendment, while the content of Fe-Mn oxidizable speciation of copper decreased. The addition of CA promoted the chemical conversion of copper from Fe-Mn oxidizable speciation to carbonate speciation in rhizoshpere soil. It concluded that EDTA significantly improved the copper uptake ofA. retroflexus and increased the content of total copper in rhizosphere soil, which resulted from the joint effects of the increasing migration activity of Cu-EDTA and the copper exclusion mechanisms ofA. retroflexus.%为明确反枝苋(Amaranthusretroflexus L.)对Cu的富集能力及EDTA与柠檬酸(CA)对Cu迁移的影响,采用盆栽试验,在0、100、200、400、800 mg·kg-1 Cu处理质量分数及2.5 mmol·kg-1 EDTA和柠檬酸施加条件下,测定了根际土、非根际土Cu不同形态含量及反枝苋组织Cu富集特征.结果表明:Cu处理质量分数小于400 mg·kg-1时,重金属Cu组织富集特征为根>叶>茎,Cu处理质量分数在400 mg·kg-1时,富集特征为根>茎>叶,Cu各处理组BCF与TF均小于1,不具备Cu超富集植物特征;EDTA、柠檬酸均可促进反枝苋对土壤中Cu的富集,并强化Cu由根系向地上部分的转移.EDTA的促进作用远高于柠檬酸,在Cu 800 mg·kg-1,施EDTA处理组反枝苋地上部分Cu可达3513 mg·kg-1.施加EDTA可增加根际土全Cu含量,显著减少根际土中Fe-Mn态Cu含量,增加Exch态,促使Fe-Mn态向Exch态的转化;柠檬酸处理的根际土中则以Fe-Mn态向Carb态转化为主.由此可见,在EDTA强化修复下,反枝苋富集Cu的能力明显增加,而根际土中Cu全量的增加,是Cu-EDTA迁移活性极大增加与反枝苋防御性Cu阻隔共同作用的结果.
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