[Cd uptake and accumulation in grains by hybrid rice in two paddy soils: interactive effect of soil type and cultivars].

Cd translocation through soil-food crop-diet is considered as one of most important pathway for human Cd exposure. Rice is considered as a particular crop with high Cd uptake and accumulation in grains among the main food crops. In this study, a pot experiment was conducted to elucidate mutual interaction of soil and cultivars on uptake and grain accumulation of Cd by hybrid rice with or without Cd spiking at 2.5 mg x kg(-1) under continuous submerging condition. Two hybrid rice cultivars (Shanyou 63, a common hybrid rice and II Youming 86, a super-rice) and two paddy soils (a Wushantu, Gleyic Stagnic Anthrosols and a Hongshanitian, Ultic Stagnic Anthrosols) were used. The results show significant differences in Cd uptake and grain partitioning between soils, cultivars and the soil-cultivar interactions. The cultivars effect on uptake of indigenous soil Cd seems stronger than the soil effect while soil effect turns significant over that of cultivars on spiked Cd. However, intense Cd accumulation in grains is found under the positive interaction of soil with high Cd availability and cultivar with high Cd affinity (super rice on acidic paddy soil). This study demonstrates a phenomenon of intense Cd uptake and grain accumulation by super rice and, thus, imposing a very high Cd exposure risk (as several times as the acceptable daily intake, ADI) to subsistence-diet farmers. The low Cd cultivar Shanyou 63 tends to hamper the up-taken Cd in root while the super rice II Youming 86 promotes higher partitioning to grain. Furthermore, the difference in total biomass between the two cultivars is small compared to that in total Cd uptake under Cd spiking. It is suggested that the Cd uptake behavior should be taken into account in super rice breeding and practical measures should be taken while spread of super rice cultivars in rice areas with acidic soils and under Cd pollution in order to control the human Cd exposure by diet.

[Effect of submerging and wetting-redrying on Cd speciation and uptake by Sorghum hybrid Sudangrass in two paddy soils under spiked Cd].

Effect of continuous submerging and wetting-redrying on cadmium speciation and uptake by Sorghum hybrid Sudangrass in a Ferric-accumulic Stagnic Anthrosol and a Tipical Hapludult collected from the Taihu Lake region and the rolling downs of Yingtan, Jiangxi, China respectively, was studied by pot experiment with Cd spike in 2003. Compared to that under wetting-redrying treatment, the MgCl2-extracted pool of Cd in Huangnitu with spiked Cd of 5mg x kg(-1) and 10mg x kg(-1) was decreased from 21.8% and 28.5% to 8.0% and 16.9% while NH2OH x HCl-extracted pool increased from 17.7% and 17.3% to28.1% and 37.5% under continuous submerging. However, in the Typical Halpudult, NaAC-extracted pool of Cd decreased from 20.8% and 29.6% to 11.6% and 12.6%. Cd uptake by Sorghum hybrid Sudangrass was found in negative correlation with the MgCl2 extracted pool of Cd. Total Cd uptake was significantly reduced by the pretreatment of continuously submerging in Huangnitu.