The impact of iron plaque on La and Nd uptake and translocation in rice (Oryza sativa L.)

The effect of root surface iron plaque formation on the uptake, transfer and accumulation of La and Nd in the rice root system was evaluated by using solution cultures. The results showed that La and Nd pollution stress inhibit formation of rice root surface iron plaques. The amount of La and Nd absorbed by the rice root surface iron plaque rose with the increase of La and Nd solution concentrations. Iron plaque formation on the rice root surface significantly decreases the La and Nd concentrations in rice roots and shoots. At growth solution La concentrations of 0.1, 0.5, and 1.0 mmol.L− 1, concentrations of La in rice roots with induced iron plaques decreased by 17.1%, 37.4%, and 31.2%, respectively, and concentrations of La in rice shoots decreased by 43.9%, 60.6%, and 27.0%, respectively, when compared to plants with non-induced iron plaques. Also, with Nd solution concentrations of 0.1, 0.5, and 1.0 mmol.L− 1, the Nd concentrations in rice roots and shoots of plants with induced iron plaques decreased by 21.0-31.7% and 22.7-47.5%, respectively when compared to plants with non-induced iron plaques. Iron plaque formation on the rice root surface affects the accumulation and transfer of La and Nd in rice roots. Accumulation of La and Nd was greater in rice roots than in rice shoots regardless of whether the plants had induced or non-induced iron plaques. Transfer coefficients of iron plague on rice root surface and root system under La treatments were both higher than those under Nd treatment. For rice roots and iron plaques on the root surface, the enrichment coefficient in the La treatment group was less than that in the Nd treatment group, while for rice shoots, the enrichment coefficient in the La treatment group was greater than that in the Nd treatment group. Clearly, the mechanisms governing the effect of iron plaque on La and Nd uptake and transfer in the rice root system are rather complicated.