蓖麻对土壤铜的超富集机理及其影响因素

Copper is nutritional element for plant growth, whereas at high content, it becomes one of the most popular polluted elements in soil. Hyperaccumulation of Cu by plants has been considered as one of the best technologies for remediation to soils contaminated by copper, and it has affected mobility and toxicity of Cu in soil. Castor (Ricinus communis L.) has big biomass and can grow well at soils with poor nutrients, and it has better economic values. Our earlier research found that castor (Ricinus communis L.) not only could grow well at soils with high contents of copper, but also accumulated Cu in its body. Based on the results from earlier study, this project will study following aspects using Cu contaminated soil in Tonglvshan mine region of Daye city, Hubei province, and castor (Ricinus communis L.) grown in this area. (1) To study the cell micro structure and Cu position in castor (Ricinus communis L.), and analyze the Cu micro zone at subcell and chemical species; (2) To extract and determine the organic acids, free amino acids exudated from root of castor (Ricinus communis L.), and illustrate the relations between root exudates and Cu hyperaccumulation through XAS, AFM and ATR-IR etc. (3) To carry out pot cutivation experiments at different fertilizations and rhizosphere micro-environments, then separate and purify Cu binding protein of castor (Ricinus communis L.) grown at Cu stress or not. After comparing the properties of these binding proteins, we try to find out the special Cu binding protein in castor (Ricinus communis L.). These results will explain the mechanism of castor (Ricinus communis L.) to detoxicity of copper, then provide the basis for studying the tolerence of castor (Ricinus communis L.) to Cu stress and using this as remediation plant at Cu contaminated soils.

Cu是矿区土壤中重要的污染元素，其被超富集植物吸收影响到土壤Cu污染治理及毒性。蓖麻生物量大、耐瘠薄、经济价值较高。我们前期研究表明，蓖麻不仅能在Cu含量很高的土壤上生长，且体内能富集Cu，是一种新发现的超富集植物。本项目在前期研究基础上，以湖北大冶铜绿山铜污染土壤和矿山蓖麻为研究对象，分析Cu在蓖麻的亚细胞微区分布及化学形态；提取并测定蓖麻根际土壤有机酸、游离氨基酸含量及其Cu分组，借助XAS、AFM、ATR-IR等仪器探讨Cu富集机理，阐明根分泌物与Cu吸收积累的关系；通过施肥和其它改变根际微环境的措施进行盆栽试验，研究铜的形态转化与其在土壤-蓖麻体内的迁移特征，分离纯化未污染和Cu胁迫下蓖麻细胞内能与Cu结合的蛋白，并比较其异同，鉴定蓖麻Cu专性结合蛋白。通过研究揭示蓖麻对Cu的解毒机理，为深入研究蓖麻Cu耐性机制及其应用于修复Cu污染土壤提供依据。

Cu是矿区土壤中重要的污染元素，蓖麻生物量大、耐瘠薄、经济价值较高。本项目以湖北大冶铜污染土壤和矿山蓖麻为研究对象，分析Cu在蓖麻的亚细胞微区分布及化学形态；提取并测定蓖麻根际土壤有机酸、游离氨基酸含量及其Cu分组，探讨Cu富集机理，阐明根分泌物与Cu吸收积累的关系；通过施肥措施，研究铜的形态转化与其在土壤-蓖麻体内的迁移特征，分离纯化Cu胁迫下蓖麻细胞内Cu结合蛋白，为研究蓖麻Cu耐性机制及其应用于修复Cu污染土壤提供依据。.研究结果表明：（1）根是蓖麻积累Cu的主要器官。蓖麻根细胞内67.7%的Cu结合在细胞壁的可交换酸性极性化合物、纤维素和木质素的结构团及蛋白质、果胶等组分上，细胞质和细胞核中结合的Cu相对较少。（2）蓖麻根分泌物中含有草酸、苹果酸、乳酸、柠檬酸和酒石酸等有机酸，且草酸含量最高。（3）Cu胁迫对土壤酸性磷酸酶活性表现为激活作用，对土壤脲酶、过氧化氢酶和蔗糖酶活性有抑制作用。土壤酸性磷酸酶可能在蓖麻根系吸收和转运Cu的过程中起到重要的促进作用。（4）Cu胁迫下蓖麻根系分泌有机酸中，草酸、苹果酸和乳酸与植株Cu含量达显著正相关，可能对蓖麻Cu吸收起到促进作用。（5）以矿区蓖麻根际土壤为分离源，分离筛选出5株耐Cu细菌和5株耐Cu真菌，鉴定了它们的属种。（6）施磷后，蓖麻地上部和地下部的铜含量均高于对照处理，即施磷促进蓖麻对铜的吸收；随着施磷量增加，地下部铜含量增加且远高于地上部；根际土和非根际土中铜的总量比种植前土壤铜含量低。蓖麻根部Cu含量随着N处理浓度的升高而显著降低，地上部随着N-NH4+处理浓度的升高而升高，随着N-NO3-处理浓度的升高而降低。与CK相比，S显著增加了蓖麻根部的Cu含量，同时降低了蓖麻茎中Cu的含量，但是S处理对蓖麻叶片中的Cu含量没有显著影响。（7）根部Cu主要是精氨酸铜、柠檬酸铜和氧化铜；茎中主要是谷胱甘肽结合铜、氧化铜和谷氨酸铜；叶片Cu主要是以精氨酸铜、柠檬酸铜、氧化铜和谷胱甘肽结合铜形态存在。这些结果对阐明蓖麻耐铜机理和利用蓖麻修复铜污染土壤有重要借鉴意义。