Antimony (Sb) is considered to be phytotoxic for plants. In the environment it exists mainly in inorganic forms as antimonite [Sb(III)] and antimonate [Sb(V)] with little organic methylated species. Its distribution dramatic increases as a result of its rapid growth in industrial use. Selenium (Se) is considered beneficial at low dosage to plants as an antioxidant and it can inhibit the uptake of various heavy metals.

The aim of this study is to investigate uptake, translocation, speciation of Sb in rice plants Se-biofortified or not, exposed to Sb(III) and Sb(V) at increased concentrations under hydroponic condition. At the same time, how Se influences/is influenced by the different Sb concentrations in the distribution of organic (SeCys₂, SeMeSeCys and SeMet) and inorganic forms [Se(IV), Se(VI)] of selenium from roots to leaves, together Malondialdehyde (MDA) content as indicator of physiological status during plant growth. Oryza sativa L. grains were chosen for the hydroponic experiments. After Se-biofortification, at rice plants seedlings was added SbCl₃ and other plants with SbCl₅ at 5 different dosages (0, 1, 3, 9 and 27 mg L^-1). Lyophilized and mineralized aboveground and the root samples were analysed by ICP-MS for total Se and Sb concentrations. Other macro elements (Ca, K, Na, Mg, Mn, Cr, Fe, Cu, As and Ni) were analysed by ICP-OES. Speciation of Sb and Se was performed by HPLC-ICP-MS on anion and cation exchange columns.

MDA analysis on fresh materials confirm the role of antioxidant of Se at low dosage with low results in root and aboveground. The high-dose of Se used for biofortified roots and sprouts had significant biomass reductions even in the absence of Sb, while the low-dose ones showed not significantly different results from the control even in the presence of Sb. Sb, with or without the addition of Se, was accumulated more in the roots. Sb, present in aqueous solution such as Sb(III), was accumulated in the roots more than the Sb present in aqueous solution such as Sb(V). Se seemed to promote of Sb(III) store in the roots, Sb(V) showed a lower accumulation in the Se-enriched roots. In the leaves, the effect of Se as antagonist element of Sb was appreciable at intermediate concentrations of Sb (3 and 9 mg L^-1). Sb(V) was the predominant specie in rice plants (79 to 93%). 9.3% of Sb(III) were found in roots and leaves when the amount of Sb increases in hydroponic solution. Chromatographic separation revealed the presence of unknown organic forms of both Sb and Se. Se underwent changes in the distribution of its chemical forms, especially organic, in the plant. Heterogeneity of the organic forms of Se in the roots, especially SeMeSeCys and Met, were in the plant roots at low Sb content. When the concentration of Sb increases, the organic forms of Se decreased in the roots and increase in the leaves, the percentages of SeMeSeCys and Met increase up to 20 and 30% of the sum of all Se species, respectively.

Additional considerations may be included in the study, monitoring Sb speciation in the medium and in short-term experiments, for the instability of Sb(III) by isotopic dilution analysis.