Influence of mycorrhizal inoculation on the accumulation and speciation of selenium in maize growing in selenite and selenate spiked soils

Effects of inoculation with arbuscular mycorrhizal (AM) fungus Glomus mosseae on the accumulation and speciation of selenium (Se) in maize were systematically investigated using soil spiked with selenite (Se(IV)) and selenate (Se(VI)). Selenium speciation was analyzed by HPLC–ICP-MS. The results indicated that accumulation and speciation of Se in plants and the influence of mycorrhizal inoculation depend on the chemical form of Se that the soil was spiked with. There was no obvious influence of inoculation on Se species distribution, plant uptake and translocation for the experimental treatment that was supplied with Se(VI). When Se(IV) was supplied to the soil, mycorrhizal inoculation promoted oxidation of Se(IV) to Se(VI) in the soil, inhibited Se accumulation by maize, enhanced the accumulation of Se(VI) but reduced the accumulation of organic Se in maize. Microbeam X-ray fluorescence (μ-XRF) mapping confirmed that mycorrhizal inoculation inhibited the translocation of Se from the surface to the inner of roots when Se(IV) was added to soil. This study elucidates, for the first time, the speciation-dependent influence of mycorrhizal inoculation on the behavior of Se in the soil–plant system.