镉在钻叶紫菀中的生物富集、亚细胞分布及化学形态研究

Bioaccumulation,subcellular distribution and chemical forms of cadmium in Aster subulatus Michx

  • 摘要: 【目的】分析镉(Cd)在钻叶紫菀中的生物富集能力、亚细胞分布及化学形态,为揭示钻叶紫菀对Cd的耐受机制提供参考依据。【方法】在Hoagland营养液及不同浓度(0、30、60和90 mg/L)Cd作用下培养钻叶紫菀,24 d后收获钻叶紫菀。钻叶紫菀叶、茎和根经差速离心、化学试剂萃取及石墨消解处理后,利用原子吸收光谱仪测定其Cd含量。【结果】钻叶紫菀Cd生物富集能力表现为根>茎>叶,钻叶紫菀根、茎和叶中的最大Cd含量分别为130.74、78.69和56.62mg/kg(鲜重)。钻叶紫菀根和叶中大部分Cd储存在细胞壁和细胞可溶性组分,仅有少量Cd储存在细胞器组分。钻叶紫菀根中细胞可溶性组分Cd占根亚细胞组分Cd的52.27%~58.61%,而钻叶紫菀叶中细胞壁组分Cd占叶亚细胞组分Cd的42.10%~63.28%。钻叶紫菀根与叶中果胶和蛋白质结合形态Cd含量高于其他化学形态Cd含量。果胶和蛋白质结合形态Cd是钻叶紫菀根和叶中存在的主要化学形态Cd,占比分别为68.91%~74.80%和57.38%~83.80%。随着培养基Cd浓度的增加,钻叶紫菀根中水溶性有机酸Cd占比由13.64%增至22.72%,同时叶中不溶性磷酸Cd占比由10.02%增至32.78%。【结论】钻叶紫菀根、茎和叶对Cd有较强生物富集能力,Cd主要储存在钻叶紫菀根细胞可溶性组分和叶细胞壁组分,且根和叶中的化学形态Cd以毒性弱的果胶和蛋白质结合形态Cd为主,这可能是钻叶紫菀耐受Cd的主要机制。

     

    Abstract: 【Objective】Through analyzing the bioaccumulation capacity,subcellular distribution and chemical forms of cadmium(Cd)in Aster subulatus Michx.,this study was to provide reference for revealing the Cd tolerance mechanism of A. subulatus Michx.【Method】After cultured for 24 d under the action of Hoagland nutrient solution and gradient Cd concentrations(0,30,60 and 90 mg/L),A. subulatus Michx. were harvested,and its leaf,stem and root were treated by differential centrifugation,chemical reagent extraction,and digested with graphite digester,respectively,then the Cd content in the root,stem and leaf were determined by atomic absorption spectroscopy.【Result】The experimental results indicated that the bioaccumulation capacity of Cd in A. subulatus Michx. was root>stem>leaf,and the maximum Cd concentration in the root,stem and leaf of A. subulatus Michx. were 130.74,78.69 and 56.62 mg/kg(fresh matter),respectively. Most of Cd stored in the cell wall and the soluble fractions of the root and leaf of A. subulatus Michx.,with only a smaller portion Cd in organelle fraction. Analysis result of subcellular Cd content showed that 52.27%-58.61% of Cd for root was mainly stored in the soluble fraction,but 42.10%-63.28% of Cd for leaf was mainly stored in the cell wall fraction. The concentration of pectates and protein integrated-Cd was higher in the root and leaf compared to other chemical forms Cd. Pectates and protein integrated-Cd was the main chemical forms Cd in the root and leaf of A. subulatus Michx., and their percentages were 68.91%-74.80% and 57.38%-83.80%,respectively. Cd treatment could significantly increase the proportion of water-soluble organic acid Cd from 13.64% to 22.72% in root and undissolved phosphate Cd from 10.02% to 32.78% in leaf with increasing Cd concentration in the culture medium.【Conclusion】The root,stem and leaf of A. subulatus Michx. has strong bioaccumulation capacity to Cd,Cd is primarily stored in the soluble fractions of the root and cell wall fractions of the leaf,and less toxic pectates and protein integrated-Cd is the main chemical forms Cd in the root and leaf of A. subulatus Michx.,this might be the main mechanism of Cd tolerance in A. subulatus Michx.

     

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