Yan Dafang, Ma Wei, Song Xiaojing, Bao Yanyu
Key Laboratory of Pollution Processes and Environmental Criteria (Ministry of Education)/Tianjin Key Laboratory of Environmental Remediation and Pollution Control, College of Environmental Science and Engineering, Nankai University, Tianjin, 300071, People's Republic of China.
Environ Sci Pollut Res Int. 2017 Mar;24(8):7544-7554. doi: 10.1007/s11356-017-8368-z. Epub 2017 Jan 23.
Although the role of iron plaque on rice root surface has been investigated in recent years, its effect on antibiotic uptake remains uncertain. In the study, pot experiment was conducted to investigate the effect of iron plaque on uptake and translocation of norfloxacin (adding 10 and 50 mg·kg treatments) in rice seedlings grown in paddy soil. Iron plaque was induced by adding different amounts of Fe(II) in soil. The results showed that the presence of norfloxacin can decrease the amount of iron plaque induced. After rice with iron plaque induced, norfloxacin was mainly accumulated in iron plaque on root surface, followed by inside root, but its translocation from root to other rice tissues is not observed. Iron plaque played the role of a barrier for norfloxacin uptake into rice roots under high norfloxacin concentration of 50 mg·kg, however not that under low concentration of 10 mg·kg. And the barrier function was the most strongest with adding Fe(II) of 30 mg·kg as combined action of iron plaque and rhizosphere effect. Fluorescence microscope analysis showed that norfloxacin mainly distributed in the outside of root cell, which showed its translocation as apoplastic pathway in rice. Comparing with non-rhizosphere, more norfloxacin was accumulated in rhizosphere soil. Maybe, strong root oxidization (high Eh values) induced more iron oxide formation in rhizosphere and on root surface, which led to norfloxacin's mobility towards to rhizosphere through its strong adsorption of iron oxides and then promoted its uptake by rice on root surface.
尽管近年来已对水稻根表面铁膜的作用进行了研究，但其对抗生素吸收的影响仍不确定。在本研究中，进行了盆栽试验，以研究铁膜对水稻土中生长的水稻幼苗吸收和转运诺氟沙星（添加10和50 mg·kg处理）的影响。通过在土壤中添加不同量的Fe(II)诱导形成铁膜。结果表明，诺氟沙星的存在会减少诱导形成的铁膜量。诱导形成铁膜后的水稻，诺氟沙星主要积累在根表面的铁膜中，其次是根内部，但未观察到其从根向水稻其他组织的转运。在诺氟沙星浓度为50 mg·kg的高浓度下，铁膜对诺氟沙星进入水稻根起到了屏障作用，但在10 mg·kg的低浓度下则没有。并且在添加30 mg·kg Fe(II)时，由于铁膜和根际效应的共同作用，屏障功能最强。荧光显微镜分析表明，诺氟沙星主要分布在根细胞外部，这表明其在水稻中的转运途径为质外体途径。与非根际相比，根际土壤中积累了更多的诺氟沙星。也许，强烈的根系氧化作用（高Eh值）导致根际和根表面形成更多的铁氧化物，这使得诺氟沙星通过其对铁氧化物的强烈吸附而向根际移动，进而促进水稻在根表面对其的吸收。
