蚕豆对铯的吸收蓄积及亚细胞分布研究

Tissue Accumulation and Subcellular Distribution of Cesium in Vicia Faba

采用改良水培法培养蚕豆幼苗至2片真叶,置于含铯(ρ(Cs+)8.24(CK)~200 mg·L^(-1))的营养液中处理7 d、14 d、21 d后取样。采用差速离心法分离亚细胞组分,采用原子吸收分光光度法测定根、茎、叶及各亚细胞组分的Cs+含量,分析蚕豆幼苗对Cs+的吸收蓄积及亚细胞分布特点,研究蚕豆对Cs+的富集转运特征及耐受机理。结果显示:蚕豆3种器官对Cs+的蓄积量为根>叶>茎,根对Cs+的蓄积量占总量的65.13%~83.17%,最高(ρ(Cs+)200 mg·L^(-1)时)达到518.40 mg·kg^(-1)FW(7 d)、1 949.74 mg·kg^(-1)FW(14 d)和3 614.03 mg·kg^(-1)FW(21 d);蚕豆根、茎、叶中Cs+的亚细胞分布主要集中在细胞壁和可溶性组分中,Cs+相对含量分别达到75.84%~99.06%(根)、79.06%~100%(茎)、82.95%~100%(叶);细胞核、前质体、叶绿体和线粒体等细胞器仅含少量的Cs+(<25%)。结果表明,蚕豆根、茎、叶细胞主要通过阻滞作用,将Cs+结合固定在细胞壁,并将进入细胞质基质的一部分Cs+转运到液泡内,暂时或"永久性"存贮,有效降低了细胞器、胞质溶胶(cytosol)及内含物中的Cs+含量,极大地减缓了Cs+对细胞器的功能性损伤,这是短期内蚕豆未表现出明显中毒症状的原因,也是蚕豆耐受Cs+胁迫的重要机理之一。

This study examined the characteristics of Cs＋accumulation and transportation, and the tolerance mechanism adopted by Vicia faba L. under Cs＋stress. Seedlings at the two leaf stage were subjected to varing doses of Cs＋（ρ（Cs＋） 8.24（control） ~ 200 mg·L^（-1）） for 7, 14 and 21 days to investigate the effects on uptake, organ accumulation, and subcellular distribution of Cs＋by differential centrifugation and atomic absorption spectroscopy. The accumulation of Cs＋in plant organs displayed the following sequence： root〉 leaf〉 stem, 65.13% ~ 83.17% of the Cs＋was in the root. The highest accumulation levels of Cs＋in the root were as much as 518.40 mg·kg^（-1）FW（7 d）,1 949.74 mg·kg^（-1）FW（14 d）, and 3 614.03 mg·kg^（-1）FW（21 d） when ρ（Cs＋） was 200 mg·L^（-1）. Subcellular distribution showed that 75.84% ~ 99.06% of the Cs＋was in the roots, 79.06% ~ 100% in the stems, and 82.95% ~100% in the leaves, and was localized in the cell walls and soluble fractions. Cs＋accumulation was less in organelles（including the nucleus, chloroplast/proplastid and mitochondrion）; this content was less than 25%. Most of the Cs＋was adsorbed onto the cell wall by the way of retardation, the portion of Cs＋in the cytosol was transported into vacuoles for provisional or permanent storage. Thus, the Cs＋content in organelles was effectively reduced, while the damage risk from Cs＋to organelles was greatly retarded. Thus, the cell walls and vacuoles may contribute jointly to the Cs＋accumulation and tolerance in Vicia faba.