College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, 210095, China.
Environ Sci Pollut Res Int. 2013 Dec;20(12):8947-54. doi: 10.1007/s11356-013-1855-y. Epub 2013 Jun 8.
The rhizosphere plays an important role in altering cadmium (Cd) solubility in paddy soils and Cd accumulation in rice. However, more studies are needed to elucidate the mechanism controlling rice Cd solubility and bioavailability under different rhizosphere conditions to explain the discrepancy of previous studies. A rice culture with nutrient solution and vermiculite was conducted to assess the effects of pH, Eh, and iron (Fe) concentration on Cd, Fe fractions on the vermiculite/root surface and their uptake by rice. The solution pH was set from 4.5 to 7.5, with additions of Fe (30 and 50 mg L(-1)) and Cd (0.5 and 0.9 mg L(-1)). At pH 5.5, the Eh in the rice rhizosphere was higher whereas transpiration, Cd(2+), and Fe(2+) adsorption on the vermiculite/root surface and accumulation in rice were lower than the other pH treatments. Cadmium addition had no impact on pH and Eh in rice rhizosphere while Fe addition decreased pH and increased Eh significantly. Compared with control, Fe addition resulted in the decrease of rhizosphere Cd, Fe solubility and bioavailability. Higher redox potential in the rice rhizosphere resulted in the decline of transpiration, Cd, and Fe accumulation in the rice tissues, suggesting that the transfer of two elements from soil to rice was depressed when the rhizosphere was more oxidized.
根际在改变水稻土中镉（Cd）的溶解性和水稻对镉的积累方面起着重要作用。然而，需要更多的研究来阐明不同根际条件下控制水稻Cd 溶解性和生物有效性的机制，以解释先前研究的差异。通过营养液和蛭石培养水稻的方法，评估了 pH、Eh 和铁（Fe）浓度对 Cd、Fe 形态在蛭石/根表面的影响及其被水稻吸收的情况。溶液 pH 值设置为 4.5 至 7.5，并添加 Fe（30 和 50 mg L(-1)) 和 Cd（0.5 和 0.9 mg L(-1))。在 pH 5.5 时，水稻根际的 Eh 较高，而蒸腾作用、Cd(2+)和 Fe(2+)在蛭石/根表面的吸附以及在水稻中的积累均低于其他 pH 处理。Cd 的添加对水稻根际的 pH 和 Eh 没有影响，而 Fe 的添加则显著降低了 pH 值并增加了 Eh 值。与对照相比，Fe 的添加降低了根际 Cd 和 Fe 的溶解性和生物有效性。水稻根际较高的氧化还原电位导致蒸腾作用、Cd 和 Fe 在水稻组织中的积累减少，这表明当根际更氧化时，两种元素从土壤向水稻的转移受到抑制。
