School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, PR China.
School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, PR China.
Environ Pollut. 2020 May;260:114048. doi: 10.1016/j.envpol.2020.114048. Epub 2020 Jan 23.
Selenium (Se) is an essential micronutrient for animals with a narrow margin between essentiality and toxicity. Se toxicity is largely related to inorganic forms of Se in soil, i.e., selenite and selenate that enter food chains through plant uptake, threatening higher trophic level organisms. This experiment investigated effects of earthworm activity on Se bioavailability in soil and the subsequent plant uptake, using earthworm Eisenia fetida and bean plant Phaseolus vulgaris L, both exposed to either selenite or selenate at 1 or 4 mg Se kg for 16 weeks. Plants took up selenate (up to 221-fold) faster than selenite, with up to 84% of the Se rapidly transported to shoots. In the presence of earthworms, Se accumulation obviously increased for selenate-supplied plants, leading to an up to 4% increase in Se translocation factor for all treatments except for 1 mg kg selenite treatment. Earthworms also concentrated Se faster in tissues (up to 274 mg kg DW) at exposure to selenate. For Se toxicity, Se speciation analysis was conducted on the plants and earthworms using XAS. Compared to worm-free treatments, the percentage of organo-Se, i.e., SeMet and CysSeSeCys, increased in beans (up to 34%) in the presence of earthworms for selenate, while the elemental Se portion was significantly reduced or absent, opposite to the results for selenite. Surprisingly, elemental Se (up to 65%) dominated earthworms, regardless of the form of Se supplied. In conclusion, earthworms clearly enhanced Se uptake and translocation in plants, leading to elevated Se levels in shoots. To prevent resulting hazards to humans and other animals, caution should be taken while consuming the shoots, particularly beans, harvested from the Se contaminated soil where earthworm activity is high. Finally, the significant reduction in soil Se suggests phytoextraction of Se from the soil could be improved using earthworms as an aid to plants.
硒（Se）是动物必需的微量元素，其必需性和毒性之间的差距很小。硒毒性主要与土壤中的无机硒形式有关，即通过植物吸收进入食物链的亚硒酸盐和硒酸盐，威胁到更高营养级的生物。本实验采用赤子爱胜蚓（Eisenia fetida）和菜豆（Phaseolus vulgaris L.）研究了蚯蚓活动对土壤中硒生物有效性的影响，以及随后植物对硒的吸收，实验中蚯蚓和植物分别暴露于亚硒酸盐或硒酸盐中，浓度为 1 或 4 mg Se kg-1，暴露时间为 16 周。植物对硒酸盐的吸收速度（高达 221 倍）快于亚硒酸盐，高达 84%的硒迅速转运到地上部分。在有蚯蚓存在的情况下，施硒酸盐的植物中硒的积累明显增加，导致除 1 mg kg-1亚硒酸盐处理外，所有处理的硒迁移因子增加了 4%。蚯蚓在暴露于硒酸盐时，也更快地在组织中浓缩硒（高达 274 mg kg-1 DW）。对于硒毒性，使用 XAS 对植物和蚯蚓中的硒进行了形态分析。与无蚯蚓处理相比，在蚯蚓存在的情况下，施硒酸盐的豆科植物中有机硒（即硒代蛋氨酸和半胱氨酸硒代半胱氨酸）的比例增加（高达 34%），而元素硒的比例显著降低或不存在，与亚硒酸盐的结果相反。令人惊讶的是，无论硒的形式如何，元素硒（高达 65%）在蚯蚓中占主导地位。总之，蚯蚓明显增强了植物对硒的吸收和转运，导致地上部分硒含量升高。为了防止对人类和其他动物造成危害，在食用从蚯蚓活动活跃、硒污染土壤中收获的植株时应格外小心，特别是豆类。最后，土壤中硒的显著减少表明，使用蚯蚓作为植物的辅助物可以改善从土壤中植物提取硒。
