Characteristics of cadmium uptake in two contrasting ecotypes of the hyperaccumulator Thlaspi caerulescens

被引:287
作者
Zhao, FJ [1 ]
Hamon, RE
Lombi, E
McLaughlin, MJ
McGrath, SP
机构
[1] IACR rothamsted, Agr & Environm Div, Harpenden AL5 2JQ, Herts, England
[2] CSIRO Land & Water, Glen Osmond, SA 5064, Australia
基金
英国生物技术与生命科学研究理事会;
关键词
Cd; hyperaccumulation; Thlaspi caerulescens; uptake; Zn;
D O I
10.1093/jexbot/53.368.535
中图分类号
Q94 [植物学];
学科分类号
071001 ;
摘要
Uptake of Cd and Zn by intact seedlings of two contrasting ecotypes of the hyperaccumulator Thlaspi caerulescens was characterized using radioactive tracers. Uptake of Cd and Zn at 2degreesC was assumed to represent mainly apoplastic binding in the roots, whereas the difference in uptake between 22degreesC and 2degreesC represented metabolically dependent influx. There was no significant difference between the two ecotypes in the apoplastic binding of Cd or Zn. Metabolically dependent uptake of Cd was 4.5-fold higher in the high Cd-accumulating ecotype, Ganges, than in the low Cd-accumulating ecotype, Prayon. By contrast, there was only a 1.5-fold difference in the Zn uptake between the two ecotypes. For the Ganges ecotype, Cd uptake could be described by Michaelis-Menten kinetics with a V-max of 143 nmol g(-1) root FW h(-1) and a K-m of 0.45 muM. Uptake of Cd by the Ganges ecotype was not inhibited by La, Zn, Cu, Co, Mn, Ni or Fe(II), and neither by increasing the Ca concentration. By contrast, addition of La, Zn or Mn, or increasing the Ca concentration in the uptake solution decreased Cd uptake by Prayon. Uptake of Ca was larger in Prayon than in Ganges. The results suggest that Cd uptake by the low Cd-accumulating ecotype (Prayon) may be mediated partly via Ca channels or transporters for Zn and Mn. By contrast, there may exist a highly selective Cd transport system in the root cell membranes of the high Cd-accumulating ecotype (Ganges) of T. caerulescens.
引用
收藏
页码:535 / 543
页数:9
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