镉在旱柳中亚细胞分布及存在的化学形态

以2个旱柳无性系幼苗为材料,通过营养液培养并结合差速离心与化学试剂提取法,分析了不同浓度Cd2+胁迫下旱柳叶和根中Cd的亚细胞分布及其存在的化学形态.结果显示,(1)随着培养介质Cd2+浓度升高,旱柳无性系幼苗叶和根中各亚细胞组分Cd含量随之增加.叶片的Cd主要富集于细胞壁、叶绿体和可溶性部分,它们的含量分别占65%～69%、14%～22%、6.8%～7.7%,仅少量Cd发现于膜部分;而根中Cd主要积累于细胞壁和可溶性部分,其中含量分别占59%～66%和14%～25%,Cd在根亚细胞组分中积累量依次为细胞壁>可溶性部分>质体>膜部分.(2)旱柳体内Cd以不同的化学形态存在,大部分为HCl(FHCl)、NaCl(FNaCl)、醋酸(HAC,FHAC)提取态,极少部分为乙醇(EtOH,FEtOH)和水提取态(Fwater),叶和根中5种Cd提取态含量依次为FHCl>FNaCl>FHAC>Fwater>FEtOH,而叶和根中HCl和NaCl提取态Cd占有比例大于30%以上.研究表明,旱柳无性系中Cd主要与蛋白质和有机酸螯合或以金属磷酸盐沉淀的形态存在,其根、叶的细胞壁和液泡在Cd忍耐与解毒中起到重要作用.

Subcellular Distribution and Chemical Forms of Cadmium in Salix matsudana

Using the differential centrifugation technique and sequential chemical extraction method,the subcellular distribution and chemical forms of Cd in Salix matsudana grown in nutrient solution were investigated.The results showed that increased Cd levels in the medium caused a significant increase of Cd concentration in all fractions of leaves and roots,most of the accumulated Cd was enriched in the cell wall (FⅠ) of leaves (65%～69%),high Cd concentration was also found in the crude chloroplastic fraction (FⅡ) (14%～22%),the cytosolic fraction (FⅣ) accumulated 6.8%～7.7% of Cd,the fraction containing the lowest level of Cd was the membrane fraction (FⅢ),Cd content in the fraction of leaves decreased in the order:FⅠ>FⅡ>FⅣ>FⅢ.The largest proportion of Cd was located in the walls of root (59%～66%).About 14%～25% of the total Cd contained in the root cells was accumulated in the soluble fraction,Cd concentration of the fractions of root decreased in the order:FⅠ(cell walls)>FⅣ(soluble)>FⅡ(trophoplast)>FⅢ(membrane fraction).The Cd concentration was bound to the different chemical forms,chemical forms of Cd (>30%) were extracted with 0.6 mol·L-1 HCl and 1 mol·L-1 NaCl in leaves and roots,the greatest amount of Cd was found in extraction solution of 0.6 mol·L-1 HCl and 1 mol·L-1 NaCl,followed by 2% HAC,and the lowest in extraction of 80% ethanol or dH2O.