两种不同镉积累类型水稻糙米中镉的存在形态(英文)

Existing Forms of Cadmium in Brown Rice(Oryza sativa L.) of Two Cultivars Differing in Cd Accumulation

采用组织化学及溶剂提取法研究了低镉积累水稻品种"广源占No.3"和高镉积累品种"珍桂矮"糙米中镉的存在形态。结果表明:镉在糙米中主要以配合物的形式存在,并且主要与蛋白质结合。在糙米主要蛋白中镉与谷蛋白和球蛋白结合量最多。与低镉积累品种"广源占No.3"相比,"珍桂矮"糙米中0.1mol/LEDTA、w=2.5%NaCl和w=0.2%NaOH提取态镉以及球蛋白中镉的比例较高,初步证明了两个品种间的差异。凝胶层析出现了3个蛋白峰(F-I,F-II和F-III),镉的出峰位置与样品流份中可溶性蛋白的出峰位置大致相同。而两种水稻品种相比较镉在3个峰中的分布有所不同。"珍桂矮"糙米可溶部分中的镉大多与相对分子质量为3 000的物质结合,属于植物鳌合肽(PCs)或低相对分子质量物质。"广源占No.3"糙米中镉与PCs配合的组分(Cd-PCs)含量远小于"珍桂矮",表明了镉在PSC和非PSC品种中分布的差异。

The existing forms of cadmium （Cd） in brown rice of two cultivars, a low-Cd accumulating cultivar Guangyuanzhan No. 3, and a high-Cd accumulating cultivar Zhenguiai, were studied through solvent extraction and biochemical methods. The results showed that Cd was mostly existed in brown rice in complex forms and mainly in the protein binding forms. Among the main proteins Cd was mainly bound with globular and glutelin. In comparison with Guangyuanzhan No. 3, Zhenguiai was higher in proportion of 0. 1 mol/L EDTA, 2.5% NaCl and 0. 2% NaOH extractable-Cd and had higher Cd percentage in globulin, which preliminary proved the difference between the two cuhivars. Three protein absorption peaks （ F-I, F-II and F-III） were identified in Tris-HCl extraction of brown rice on Sephadex G 75. The distribution of Cd in the soluble fraction followed the same elution pattern as protein. While comparing the two rice cuhivars Cd distribution in the three absorption peaks was different. In Zhenguiai the majority of soluble Cd was bounded to phytochelatins （PCs） or low-molecular-weight components with a molecular weight of- 3 kDa. However, the content of Cd-PCs in seed in the variety of Guangyuanzhan No. 3 was founded to be much lower than that in Zhenguiai, which possibly implying the difference of Cd allocation in PSC and non-PSC.