The Uptake and Accumulation of Arsenic by Paddy Rice As Affected by Iron Plaque and Variation of Genotypes.

The problem of arsenic (As)-contaminated rice affects the food safety and human health, therefore, it received more concerns in recent years around the world. A pot experiment was conducted to investigate the effects of iron plaque on root and diverse rice (Oryza sativa L.) genotypes on the uptake and accumulation of As by rice seedlings. Twenty-eight rice genotypes commonly planted in Taiwan, including both Japonica and Indica subspecies were used in this study. Rice seedlings were pre-cultivated in nutrient solutions for 12 days and then transplanted to As-contaminated soils (156 mg As kg^-1) grown for 38 days. The results showed that there were significant differences in the amounts of iron plaque (extracted by DCB solutions) deposited on root surfaces among different genotypes, and the Japonica higher than Indica. The amounts of As sequestered in iron plaques were higher than those accumulated in roots and shoots in all tested genotypes, and about 73.0 to 94.6 % of As uptake from soils were distributed in iron plaques. However, the concentrations of As in roots and shoots were not significantly correlated with the amounts of iron plaque of rice cultivars. These results indicated that the iron plaque play an important role in reducing the uptake and accumulation of As in rice plants, but the extent of retention of As by iron plaque and decrease of As uptake by rice plants were not only determined by the iron plaque formation capability of rice cultivars.