Key Laboratory of Plant Nutrition and Fertilizer, Agriculture and Rural Affairs / Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing, 100081, PR China.
Key Laboratory of Plant Nutrition and Fertilizer, Agriculture and Rural Affairs / Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing, 100081, PR China.
Chemosphere. 2020 Jul;251:126355. doi: 10.1016/j.chemosphere.2020.126355. Epub 2020 Feb 26.
Iron (Fe) in soil is closely related to cadmium (Cd) uptake by rice plants, and soil pe + pH significantly influences Fe redox behavior. This study aimed to explore the influential mechanisms of varying pe + pH conditions on the transformation of iron oxides in the rhizosphere and the subsequent effect on Cd accumulation in rice plants. A two-month pot experiment was conducted to investigate the effect of soil pe + pH on the fractions of iron oxides and formation of iron plaque (IP), as well as the effect of these changes on Cd uptake by rice plants (Oryza sativa L.). Different irrigation strategies, 70% water holding capacity (DY), continuous flooding (FL), and alternate flooding/drying weekly (AWD), were used to achieve various soil pe + pH levels. The results showed that low pe + pH conditions (under the FL and AWD treatments) were more beneficial to the transformation of crystalline iron oxides into amorphous forms in rhizosphere soil and the precipitation of IP on rice roots. The increase of amorphous iron oxides resulted in the reduction of Cd availability in rhizosphere soil by immobilizing more Cd on Fe oxides. Moreover, Cd adsorbed on rice root surfaces reacted with IP, inhibiting Cd soil-to-root transport. The two mechanisms combinatively functioned at decreasing Cd concentration in rice shoots by 14.1-33.1% at low pe + pH conditions compared to that of the high pe + pH (DY treatment). These results indicate that lowering soil pe + pH effectively reduced Cd accumulation in rice plants, probably through the immobilization of amorphous Fe oxides on Cd and sequestration of iron-plaque on Cd.
土壤中的铁（Fe）与水稻对镉（Cd）的吸收密切相关，而土壤的 pe + pH 值显著影响 Fe 的氧化还原行为。本研究旨在探索不同 pe + pH 值条件对根际氧化铁转化及其对水稻植株 Cd 积累影响的作用机制。通过为期两个月的盆栽实验，研究了土壤 pe + pH 值对氧化铁形态和铁斑（IP）形成的影响，以及这些变化对水稻植株（Oryza sativa L.）Cd 吸收的影响。采用不同的灌溉策略，即 70%水分保持能力（DY）、连续淹水（FL）和每周交替淹水/干燥（AWD），来实现不同的土壤 pe + pH 值水平。结果表明，低 pe + pH 值条件（在 FL 和 AWD 处理下）更有利于根际土壤中结晶氧化铁向无定形形态的转化和水稻根系上 IP 的沉淀。无定形氧化铁的增加通过将更多的 Cd 固定在 Fe 氧化物上，从而降低了根际土壤中 Cd 的有效性。此外，Cd 吸附在水稻根表面与 IP 反应，抑制了 Cd 从土壤到根系的运输。这两种机制共同作用，在低 pe + pH 值条件下，与高 pe + pH 值（DY 处理）相比，降低了水稻地上部 Cd 浓度 14.1-33.1%。这些结果表明，降低土壤 pe + pH 值可有效降低水稻植株对 Cd 的积累，可能是通过无定形 Fe 氧化物对 Cd 的固定和铁斑对 Cd 的螯合作用。
