毛葱的镉吸收积累及亚细胞分布特征

Characteristics of accumulation and subcellular distribution of cadmium in Allium cepa var. agrogarum

采用营养液培养法、亚细胞组分差速分离技术和电感耦合等离子体发射光谱技术(ICP-AES),研究不同浓度Cd2+(1、10、100μmol/L)胁迫下,毛葱幼苗不同部位Cd、Fe、Mn、Cu、Zn等金属元素吸收积累的特点,以及根和叶中Cd的亚细胞分布状况.结果表明:(1)随着营养液中Cd2+浓度的增加,毛葱根、茎、叶各器官中Cd的含量均显著增加,Cd主要集中在根部,向地上部分的运输量很少;(2)Cd的吸收积累改变了根、茎、叶中Fe、Mn、Cu、Zn等矿质元素的含量;(3)叶和根各亚细胞组分中Cd的含量为:细胞壁组分>细胞质可溶性组分>细胞核、叶绿体组分>线粒体组分;(4)随着营养液中Cd2+浓度的增加,细胞壁和细胞质组分中Cd增加的幅度远远大于线粒体、细胞核和叶绿体组分,Cd在细胞壁和细胞质组分中的分配比例呈上升趋势,在线粒体、细胞核及叶绿体中的比例呈下降趋势.这说明植物吸收的Cd主要积累在根部,细胞水平上,多数的Cd被细胞壁沉淀螯合和液泡区室化,避免了Cd对新陈代谢旺盛的亚细胞组分的影响.

By hydroponic experiments combined with subcellular fractionation technology and ICP-AES, the accumulation characteristics of Cd, Fe, Mn, Cu, Zn in different organs and the subcellular distribution traits of Cd in roots and leaves of Allium cepa var. agrogarum seedlings under the stress of different Cd2＋ concentrations （ 1, 10, 100μmol/L） were in- vestigated. The results showed that： （ 1 ） With the increase of Cd2＋ concentration in the nutrient solution, the cadmium in roots, stems and leaves of Allium cepa var agrogarum seedlings significantly increased, and Cd accumulated mostly in roots, which transported to aerial part very little. （2） The accumulation of Cd in AUium cepa var. agrogarum seedlings changed the contents of Fe, Mn, Cu, Zn in roots, stems and leaves. （3） The subcellular distribution of both leaves and roots fractions was as follow： cell wall composition 〉 soluble fraction cytoplasm 〉 nucleus, chloroplast components 〉 mito- chondrial components. （4） With the increase of Cd2＋ concentration in the nutrient solution, the increase degree of Cd in cell wall and soluble fraction cytoplasm was greatly larger than that in nucleus, chloroplast components, and mitocbondrial components. Meanwhile, Cd percentages in cell wall and soluble fraction cytoplasm increased generally, which in nucle- us, chloroplast components and mitoehondrial components descended. In conclusion, Cd absorbed by Allium cepa vat. agrogarum seedlings was mainly accumulated in the roots. On the cell level, much Cd was deposited and chelated by cell wall, or localized in vacuole. This can keep subcellnlar fractions metabolizing vigorously from the effect of Cd.