蚕豆对铯的吸收蓄积及亚细胞分布研究

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。

Tissue Accumulation and Subcellular Distribution of Cesium in Vicia faba

This study examined the characteristics of Cs+accumulation and transportation, and the tolerance mech-anism 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 accumula-tion , and subcellular distribution of Cs+by differential centrifugation and atomic absorption spectroscopy. The accu-mulation 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) whenρ(Cs+) was 200 mg?L-1 . Subcellular distribu-tion 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 (in-cluding 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.