在氮气冲洗下根铁斑的形成和特征及其对水稻幼苗（Oryza sativa）中锌和镉迁移的影响。
Root iron plaque formation and characteristics under N2 flushing and its effects on translocation of Zn and Cd in paddy rice seedlings (Oryza sativa).
机构信息
Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen, China.
出版信息
Ann Bot. 2013 Jun;111(6):1189-95. doi: 10.1093/aob/mct072. Epub 2013 Apr 9.
BACKGROUND AND AIMS
Anoxic conditions are seldom considered in root iron plaque induction of wetland plants in hydroponic experiments, but such conditions are essential for root iron plaque formation in the field. Although ferrous ion availability and root radial oxygen loss capacity are generally taken into account, neglect of anoxic conditions in root iron plaque formation might lead to an under- or over-estimate of their functional effects, such as blocking toxic metal uptake. This study hypothesized that anoxic conditions would influence root iron plaque formation characteristics and translocation of Zn and Cd by rice seedlings.
METHODS
A hydroponic culture was used to grow rice seedlings and a non-disruptive approach for blocking air exchange between the atmosphere and the induction solution matrix was applied for root iron plaque formation, namely flushing the headspace of the induction solution with N2 during root iron plaque induction. Zn and Cd were spiked into the solution after root iron plaque formation, and translocation of both metals was determined.
KEY RESULTS
Blocking air exchange between the atmosphere and the nutrient solution by N2 flushing increased root plaque Fe content by between 11 and 77 % (average 31 %). The N2 flushing treatment generated root iron plaques with a smoother surface than the non-N2 flushing treatment, as observed by scanning electron microscopy, but Fe oxyhydroxides coating the rice seedling roots were amorphous. The root iron plaques sequestrated Zn and Cd and the N2 flushing enhanced this effect by approx. 17 % for Zn and 71 % for Cd, calculated by both single and combined additions of Zn and Cd.
CONCLUSIONS
Blocking of oxygen intrusion into the nutrient solution via N2 flushing enhanced root iron plaque formation and increased Cd and Zn sequestration in the iron plaques of rice seedlings. This study suggests that hydroponic studies that do not consider redox potential in the induction matrices might lead to an under-estimate of metal sequestration by root iron plaques of wetland plants.
背景与目的
在水培实验中，很少考虑缺氧条件对湿地植物根铁斑诱导的影响，但这种条件对根铁斑在野外的形成是必不可少的。虽然通常会考虑亚铁离子的可用性和根径向氧损失能力，但忽略根铁斑形成过程中的缺氧条件可能会导致对其功能效应的低估或高估，例如阻止有毒金属的吸收。本研究假设缺氧条件会影响水稻幼苗根铁斑形成特征和 Zn 和 Cd 的迁移。
方法
采用水培培养方法种植水稻幼苗，并采用一种非破坏性的方法阻止大气与诱导溶液基质之间的空气交换，即在根铁斑诱导过程中用 N2 冲洗诱导溶液的顶空。在形成根铁斑后，向溶液中添加 Zn 和 Cd，并测定两种金属的迁移。
主要结果
用 N2 冲洗阻止大气与营养液之间的空气交换，使根斑 Fe 含量增加了 11%至 77%（平均增加 31%）。与非 N2 冲洗处理相比，N2 冲洗处理生成的根铁斑表面更光滑，用扫描电子显微镜观察，但铁氧化物覆盖在水稻幼苗根部呈无定形。根铁斑螯合 Zn 和 Cd，N2 冲洗通过单一和组合添加 Zn 和 Cd，使 Zn 的螯合作用增强约 17%，使 Cd 的螯合作用增强约 71%。
结论
通过 N2 冲洗阻止氧气侵入营养液，增强了水稻幼苗根铁斑的形成，并增加了 Cd 和 Zn 在铁斑中的螯合。本研究表明，不考虑诱导基质中氧化还原电位的水培研究可能会低估湿地植物根铁斑对金属的螯合作用。
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