| Cadmium is principally dispersed in natural and agricultural environments through various industrial and agricultural activities. This trace metal is a pollutant and potential toxin that has no known function in any biological organism, and is one of the most dangerous heavy metals for the environment due to its high mobility and low toxic concentration in organisms. As a core of agricultural ecosystem, soil-plant system loads chemicals and sewage, and is the key of transfer of cadmium to food chain. Therefore, controlling transfer of cadmium in the food chain through plant biotechnology and agronomic management, including reducing cadmium content in phosphoric fertilizer, increasing soil pH, improving crop rotation may be the available approach for agricultural food safety.This experiment studied differences on Cd accumulation among 85 rice (Oriza sativa L.) genotypes such as Chunjiangll, Erjiufeng, Huapei528, Hongzao, Zhenongda454 and so on, collected from the experimental farm of Huajiachi campus, Zhejiang University. The grains of all 85 rice genotypes were divided into rice husk, brown rice, polished rice and bran. Subsamples were oven dried, ashed, and cadmium concentration in the digested solution was determined by graphite furnace atomic absorption spectrometry (GFAAS). Based on the cluster analysis, typic rice genotypes were selected and used in the experiments. With the solution and soil culture experiments, genotypic defferences of cadmium uptake and accumulation in riceplants and the relative physiological mechanisms were studied. The correlations between Cd concentration in brown rice and Cd level of tested soil were investigated, as well as the criteria of soil cadmium pollution was also discussed. The main results obtained were summarized as follows:1. Subsamples such as rice husk, brown rice, polished rice and bran were prepared from grains of 85 rice genotypes. Cd concentrations of all subsamples were determined by graphite furnace atomic absorption spectrometry (GFAAS). The rice genotypes could be divided into four clusters acting on Cd concentration. It was also found that Cd concentration in polished rice of indica rice (46 genotypes) was significantly higher than that ofjaponica rice (39 genotypes), and Cd concentration in husk of indica rice is lower than that of japonica rice.2. Cd concentration in the soil for growing 85 rice genotypes is lower than the current criteria of soil cadmium pollution, but Cd concentrations in grains of the rice gehotypes were still excessive to the limit of Cd concentration in food (0.2 mg kg-1) partially. The percentage of rice genotypes with excessive Cd concentration were 15.29% for polished rice and 22.35% for brown rice. This results implied that the criteria of soil cadmium pollution should be lower than the current one (0.5 mg kg-1).3. There was a significant correlation between Cd concentration in husk and in brown rice, implying that the role of rice husk as the plant twig on controlling Cd accumulation in brown rice or polished rice is limited. As there was a significant positive correlation between Cd concentration in polished rice and in brown rice, determination and comparison one of Cd concentrations in polished rice and in brown rice for selection of rice genotypes with lower Cd accumulating potential is feasible.4. The orders of Ca and Mg concentrations in brown rice and in polished rice were contrary to the order of Cd concentrations in brown rice and in polished rice, which is probably the results of the Ca and Mg antagonism to Cd.5. Cd concentrations in roots and in plaque on root surface were significantly correlative to Fe concentrations in plaque on root surface, and Fe concentrations in plaque on root surface was significantly correlative to root oxiding activity (r=0.907**). The greater potential on Cd accumulation in rice plant is probablyrelative to higher root oxiding activity, higher Fe and Cd concentrations in plaque on root surface and higher percentage of Cd distribution in plades, which can be used as indexes to...
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