Absorption of Cd by hybrid rice under the Cd stress and its dynamic change

Cadmium(Cd) is non-essential but toxic element. It is an important agricultural pollutant in environment and farm product. It is easily absorbed and accumulated in rice grain, different rice varieties have different unique genes, resulting in the ability of Cd uptake and accumulation in rice grain differently. So, Cd-resistant characteristics of rice varieties and their transport efficiency in different growth stages are important for Cd-pollution control. Cd content in grain, Cd accumulation and its dynamic changes in different stages of rice root, stem and leaves under the Cd stress had been studied in two type of rice(D83A/R527 and Fuyou 838) by hydroponic experiments. The result showed that, the Cd content of two type of rice under Cd stress was highly significant. In 1.0 mg·L-1 Cd stress, the grain Cd concentration of Fuyou 838 had exceeded the national food safety standards. At 1.0~3.0 mg·L-1 Cd treatments, the grain Cd concentration of D83A/R527 was only 50~ 60% of Fuyou 838. With the increase of Cd treatment and the growing progress, Cd content in different parts of rice showed gradual increasing, Fuyou 838 was greater than D83A/R527. Considering about the different parts, the accumulation capacity of root was the highest, while that of leaves was the lowest, and accumulation in Fuyou 838 was higher than that of D83A/R527. The uptake of Cd in stems, leaves and accumulation efficiency of Fuyou 838 was about 1.5~ 2.0 times than that of D83A/R527. For about different growth stages, the absorption capacity of Cd in filling stage was the highest efficiency under the 1.0~3.0 mg·L-1 Cd stress, and its Cd content was largest in different parts of rice. The Fuyoou 838 had the higher Cd transfer efficiency from root to stem and leaf. The D83A/R527 had the higher Cd transfer efficiency from root to stem, but had the lower Cd transfer efficiency from stem to leaves, and the Cd accumulation in leaves was lowest. In a word, the filling stage was not only the important period during the dry matter accumulation for rice, but also was the critical period of Cd accumulation. These characteristics established the major theoretical foundation for the selecting of low Cd uptake or accumulation and controlling of Cd pollution in rice varieties.