八宝景天–柑橘间作降低柑橘根际土壤镉含量以减少对镉的吸收

Intercropping of citrus with Hylotelephium spectabile reduces Cd uptake by removing Cd in rhizosphere soil of citrus

【目的】超富集植物与经济作物间作是实现重金属污染农田边生产边修复的有效措施。为此,研究八宝景天(Hylotelephium spectabile)和柑橘间作对柑橘重金属吸收累积的影响,为柑橘生产提供安全、经济有效的栽培措施。【方法】以早熟和晚熟柑橘、八宝景天为试材进行盆栽试验,以全Cd含量为0.92 mg/kg的污染土壤和0.06 mg/kg的清洁土壤为供试土壤。分别设置早熟和晚熟柑橘单作、八宝景天单作、早熟和晚熟柑橘–八宝景天间作和柑橘–八宝景天限制性间作,共7个处理,限制性间作采用半透膜根际袋将八宝景天和柑橘根系分开。在植株生长74天(7月)和218天(12月)时采样,调查植株生物量和Cd含量,分别测定根际土壤全Cd和有效态Cd含量。【结果】与柑橘单作相比,与八宝景天间作柑橘的叶片Cd含量降低了26.7%,与清洁土壤种植的柑橘叶片Cd含量(0.011 mg/kg)相近。间作条件下,柑橘根际土壤中全Cd含量由0.92 mg/kg降低至0.75 mg/kg,有效态Cd含量由单作处理的0.82 mg/kg降低至0.78 mg/kg,低于柑橘单作处理;柑橘–八宝景天间作柑橘根际土壤中全Cd的减少量是柑橘–八宝景天限制性间作柑橘根际土壤全Cd减少量(6.52%)的2.83倍。柑橘–八宝景天间作中八宝景天对土壤Cd的年提取量、年去除率分别达1.40 mg/pot、3.34%,与其单作(1.50mg/pot、3.73%)相比,去除效率降低了10.6%,其主要原因是间作降低了八宝景天的生物量。【结论】尽管柑橘–八宝景天间作影响八宝景天对镉的去除效率,但显著降低了柑橘根际全Cd和有效态Cd含量,进而将柑橘叶片Cd含量降低到与清洁土壤下近似的水平,实现了边修复边安全生产的目标,因此,柑橘–八宝景天间作可作为中低度Cd污染农田土壤修复的重要生物措施。

【Objectives】Intercropping of hyper accumulator with cash crops is an effective measure to preventing cash crop from injury of heavy metals in contaminated soil.So,we studied the effect of H.spectabile and citrus intercropping on the absorption and accumulation of Cd by citrus in order to confirm a cost-effective measurement for safe citrus production.【Methods】Both early and late maturing citrus and HHylotelephium spectabile were used as test materials in a pot experiment,in which the total Cd content in contaminated and uncontaminated soil were 0.92 mg/kg and 0.06 mg/kg,respectively.The seven treatments included early and later maturing citrus monoculture,intercropped with H.spectabile with and without limitation of root growth space,and H.spectabile monoculture.When plants were grown for 74 days(July)and 218 days(December),taking plants and soil samples to investigate plant biomass and Cd content,soils were tested for total Cd and available Cd content,respectively.【Results】Under intercropping,the Cd content of citrus leaves decreased by 26.7%compared with that of citrus under monoculture,and had no significantly difference with that in citrus leaves grown in uncontaminated soil(0.011 mg/kg).The total and available Cd contents in intercropped citrus rhizosphere soil was significantly lower than those of monocrop citrus(P<0.05),with the total Cd from 0.92 mg/kg to 0.75 mg/kg,and the available Cd decreased from 0.82 mg/kg to 0.78 mg/kg,respectively.The reduction of total Cd in intercropped citrus rhizosphere soil was 2.83 times of that in citrus-H.spectabile restrictive intercropping(6.52%).Due to intercropping with citrus,the annual extraction and annual removal rate of soil Cd by H.spectabile were 1.40 mg/pot and 3.3%,respectively,compared with H.spectabile monoculture(1.50 mg/pot,3.7%),the removal efficiency was reduced by 10.6%.【Conclusions】Although the citrus-H.spectabile intercropping has certain negative effect on the Cd remove efficiency of H.spectabile,it significantly reduces total and available Cd contents in the citrus rhizosphere soil,so decreases the Cd contents in citrus leaves.The intercropping of citrus with H.spectabile is thus a cost-effective measurement for achieving the target of safe production and remediation of Cd contaminant at the same time.