Effect of Cd(II) and Se(IV) exposure on cellular distribution of both elements and concentration levels of glyoxal and methylglyoxal in Lepidium sativum

In this work, the effect of cadmium (0-5.0 mg L-1 as cadmium chloride, Cd(II)) and selenium (0-2.0 mg L-1 as sodium selenite, Se(IV)) was studied in Lepidium sativum with specific focus on glyoxal (GO) and methylglyoxal (MGO) and on the cellular distribution of both elements under different exposure conditions. The concentrations of two reactive alpha-ketoaldehydes present as natural metabolites and as by-products of lipid peroxidation, were increased in plants treated with Cd(II), providng complementary experimental evidence on element phytotoxicity in garden cress, in terms of oxidative damage. Even though for higher than 1.0 mg L-1 Se in medium similar adverse effect was found, under simultaneous exposure to both elements the changes in GO and MGO concentrations were clearly attenuated as compared to a single stressor treatment. This effect was accompanied by lower uptake of the two elements, significant decrease of their relative distribution in the fraction containing polar compounds and their increase in fraction corresponding to insoluble cell fragments/components, suggesting that the direct in vivo interaction between two element forms might be involved in the favorable effects of simultaneous treatment with Cd(II) + Se(IV). The fluorescence spectra obtained for biomass extracts corresponding to different exposure conditions suggested possible in vivo formation of CdSe quantum dots; however further studies are needed for ultimate identification and characterization of such nanoparticulate species.