Abstract
Plant samples of Cardamine hupingshanesis (Brassicaceae), Ligulariafischeri (Ledeb.) turcz (Steraceae) and their underlying top sediments were collected from selenium (Se) mine drainage areas in Enshi, China. Concentrations of total Se were measured using Hydride Generation-Atomic Fluorescence Spectrometry (HG-AFS) and Se speciation were determined using liquid chromatography/UV irradiation-hydride generation-atomic fluorescence spectrometry (LC-UV-HG-AFS). The results showed that C. hupingshanesis could accumulate Se to 239±201 mg/kg DW in roots, 316±184 mg/kg DW in stems, and 380±323 mg/kg DW in leaves, which identifies it as Se secondary accumulator. Particularly, it could accumulate Se up to 1965±271 mg/kg DW in leaves, 1787±167 mg/kg DW in stem and 4414±3446 mg/kg DW in roots, living near Se mine tailing. Moreover, over 70% of the total Se accumulated in C. hupingshanesis were in the form of selenocystine (SeCys2), increasing with increased total Se concentration in plant, in contrast to selenomethionine (SeMet) in non-accumulators (eg. Arabidopsis) and secondary accumulators (eg. Brassica juncea), and selenomethylcysteine (SeMeCys) in hyperaccumulators (eg. Stanleya pinnata). There is no convincing explanation on SeCys2 accumulation in C. hupingshanesis based on current Se metabolism theory in higher plants, and further study will be needed.
Highlights
Enshi is located in western Hubei province, China (Fig. 1a)
Earlier studies indicated that the soil Se concentrations varied significantly in Enshi with the highest Se concentration found in the Se mine drainage areas [4]
The highest plant Se accumulation was observed at the sampling site 3 in Creek 1 (YTB 1–6 sampling sites, see Fig. 1), showing 19656271 (n = 3) mg/kg DW in leaves, 17876167 (n = 3) mg/kg DW in stem, and 441463446 (n = 3) mg/kg DW in roots
Summary
Enshi is located in western Hubei province, China (Fig. 1a). It has the only selenium (Se) mines in the world, which were formed during the Maokou, Late Permian period. Carbon-siliceous sediment ( called ‘‘stone coal’’) contains the highest content of Se (up to 8,500 mg/kg), followed by silicon-carbonaceous sediment and peat coal [1,2]. Human activities, such as coal mining and agricultural soil amendment with coal ash, have played an important role in the transport and distribution of Se in the local environment [3]. Since the Se mine drainage areas contain high levels of bioavailable Se, it provides a unique environment to study plants with novel features on Se accumulation and biotransformation. Because methyl-SeCys does not enter proteins, it can be safely accumulated to high levels in plant tissues, which explains in part the high tolerance of hyperaccumulators to Se
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