Effects of two kinds of iron fertilizer, FeSO4 and EDTA·Na2Fe were studied on cadmium accumulation in rice plants with two rice genotypes, Zhongzao 22 and Zhongjiazao 02, with soil culture systems. The results showed that application of iron fertilizers could hardly make adverse effects on plant growth and rice grain yield. Soil application of EDTA·Na2Fe significantly reduced the Cd accumulation in rice roots, shoots and rice grain. Cd concentration in white rice of both rice genotypes in the treatment of soil application of EDTA·Na2Fe was much lower than 0.2 mg/kg, the maximal Cd permission concentra- tion in cereal crop foods in State standard. However, soil application of FeSO4 or foliar application of FeSO4 or EDTA·Na2Fe resulted in the significant increase of Cd accumulation in rice plants including rice grain compared with the control. The results also showed iron fertilizers increased the concentra- tion of iron, copper and manganese element in rice grain and also affected zinc concentration in plants. It may be a new promising way to regulate Cd accumulation in rice grain in rice production through soil application of EDTA·Na2Fe fertilizers to maintain higher content of available iron and ferrous iron in soils.
SHAO GuoSheng, CHEN MingXue, WANG DanYing, XU ChunMei, MOU RenXiang, CAO ZhaoYun & ZHANG XiuFu China National Rice Research Institute, Hangzhou 31006, China
Two indica rice genotypes, viz. Milyang 46 and Zhenshan 97B differing in Cd accumulation and tolerance were used as materials in a hydroponic system consisting of four Cd levels （0, 0.1, 1.0 and 5.0 μmol/L） and three N levels （23.2, 116.0 and 232.0 mg/L） to study the effects of nitrogen status and nitrogen uptake capacity on Cd accumulation and tolerance in rice plants. N-efficient rice genotype, Zhenshan 97B, accumulated less Cd and showed higher Cd tolerance than N-inefficient rice genotype, Milyang 46. There was consistency between nitrogen uptake capacity and Cd tolerance in rice plants. Increase of N level in solution slightly increased Cd concentration in shoots but significantly increased in roots of both genotypes. Compared with the control at low N level, Cd tolerance in both rice genotypes could be significantly enhanced under normal N level, but no significant difference was observed between the Cd tolerances under normal N （116.0 mg/L） and high N （232.0 mg/L） conditions. The result proved that genotypic differences in Cd accumulation and toxicity could be, at least in part, attributed to N uptake capacity in rice plants.
Du QinCHEN Ming-xueZHOU RongCHAO Zhao-yunZHU Zhi-weiSHAO Guo-shengWANG Guang-ming
