The Effects of Iron Plaque On Uptake and Accumulation of Cadmium by Four Rice Cultivars Grown In Solution Culture.

Iron plaque on the root surface of rice is ubiquitously. However, there have been few reports on the relationship between iron plaque and cadmium uptake by rice plants. Therefore, a hydroponic culture was conducted to investigate the effect of iron plaque on uptake and accumulation of Cd by rice seedlings. In this study, four rice cultivars (japonica cultivars: TY3, TK9 and indica cultivars: CSY962021, TS2) were used. Rice seedlings were pre-cultivated for 24 days and then transferred to hydroponic solutions with or without addition of 100 mg L^-1 Fe(II) and three levels of Cd (0, 0.1 and 1.0 mg L^-1) for 10 days. The results showed that the Fe concentrations in iron plaque (dithionite-citrate-bicarbonate (DCB)-extracts) of Fe addition treatments were significantly higher than control, but the concentration of Cd in the iron plaque (DCB-extracted) were significantly lower. Although Cd can't be effectively adsorbed on the iron plaque, but the Cd concentrations in root and shoot of Fe addition treatments were significantly lower than control at three Cd levels. All cultivars have the same trend. These results indicated that the mechanism of iron plaque to inhibit Cd uptake within the rice plants may be due to that iron plaque acts as a barrier rather than an adsorbent for Cd to reduce the uptake and accumulation of Cd by rice plants.