晚粳稻籽粒中砷、镉、铬、镍、铅等重金属含量的品种和粒位效应

 选用籽粒着粒密度差异较大的密穗型品种秀水63和散穗型品种秀水11，种植于受重金属轻度污染的土壤，研究了晚粳稻籽粒中有毒重金属As、Cd、Cr、Ni、Pb含量的品种与粒位效应。结果表明，重金属含量的粒位间差异秀水63明显大于秀水11，As、Cd、Cr、Pb含量粒位间差异显著， Ni含量差异较小。穗上部籽粒As、Cd、Ni含量高于中部籽粒，穗下部籽粒最低，而Cr、Pb则正好相反。稻米中几种重金属含量与粒重的关系因重金属种类不同存在着差异，籽粒As、Cd、Ni含量与粒重呈正相关，而Cr和Pb含量与粒重呈负相关。秀水63和秀水11不同粒位的籽粒灌浆模式存在差异，下位粒灌浆速率较低，使粒重较上、中位粒低，导致粒重有较大的粒位差异，而这种差异也与穗部着粒密度有关，秀水63明显大于秀水11。籽粒As、Cd、Ni含量与最大灌浆速率（GRm）呈正相关，与到达最大灌浆速率时间（Tpoi）呈负相关，而Cr和Pb含量与以上两个籽粒灌浆特性参数分别呈负相关和正相关，说明籽粒As、Cd、Ni的积累与碳水化合物的积累具有相同或相近的模式，而Cr和Pb表现为不同的积累模式。

Effect of Grain Position in a Panicle and Varieties on As,Cd, Cr, Ni, Pb Contents in Grains of Late japonica Rice

Two japonica rice varieties, a compact panicle type variety (CP) Xiushui 63 and a loose panicle type variety (LP) Xiushui 11, were grown in a slightly contaminated paddy field to determine the effect of grain position within a panicle and varieties on toxic heavy metal content in rice grains. There was a significant variation in heavy metal content among grains within a panicle. Furthermore, this variation varied with variety and metal. Shch as, Xiushui 63 showed higher variation than Xiushui 11, and As, Cd, Cr and Pb had a significant variation, while no significant variation for Ni. The top grains (TG) in a panicle had higher As, Cd and Ni contents compared with the middle ones (MG), and the bottom grains (BG) had the lowest. With regard to Cr and Pb, the case was opposite. The significantly positive correlations were found between grain weight and As, Cd, Ni contents in grains, but negative for grain weight and Cr, and Pb content. There was a remarkable difference in grain filling pattern among grains within a panicle, and between Xiushui 63 and Xiushui 11. In comparison with middle grains and top grains in a panicle, the bottom ones had lower grain filling rate and grain weight, leading to obvious difference in grain weight among grains within a panicle, and Xiushui 63 had significantly larger difference than Xiushui 11. There were significant and positive correlations between As, Cd, Ni content in grains and the maximum grain filling rate, but negative between the contents of these elements in grains and the time reaching the maximum grain filling rate. Concerning Cr and Pb, the case was just opposite. It is suggested that the accumulation of As, Cd and Ni is accompanied by accumulation of carbohydrates in rice grains.