Localization and speciation of selenium and mercury in Brassica juncea—implications for Se–Hg antagonism

Abstract

The occurrence and form of selenium and mercury were investigated in Indian Mustard, Brassica juncea, a selenium accumulating plant, which had been co-exposed to varying concentration levels of these two elements. Plants were grown and exposed in hydroponic solutions. Following exposure, root exudates were collected in fresh solutions and the head-space around the aerial portions of the plants was sampled. These samples and the harvested plant tissues were then processed for determination of Se and Hg-containing compounds. For the plant tissues, roots, stems and leaves were separated and extracted using a sequential procedure that removed watersoluble species, water-soluble proteins, and dodecyl sulfate-soluble proteins. Size exclusion chromatography allowed further fractionation. High molecular-weight selenium/mercurycontaining compounds were found primarily in the plant root extract. Evidence suggests that a Se and Hg complex of high molecular weight may be protein associated. For the analysis of exudate solutions, ion-pairing reversed phase chromatography coupled to ICP-MS was used. Multiple selenium and mercury species were detected, with one mercury-containing compound observed eluting near selenocystine. Plant head-space was sampled with solid phase microextraction and analyzed with GC-ICP-MS and GC-TOFMS. Apart from the primary selenium volatiles and elemental mercury, no volatile species simultaneously containing Se and Hg could be detected.

Modulation of exogenous selenium in cadmium‐induced changes in antioxidative metabolism, cadmium uptake, and photosynthetic performance in the 2 tobacco genotypes differing in cadmium tolerance

“…The present experiments have shown that Se obviously suppressed Cd accumulation in both shoots and roots. A Se-and Hg-containing compound was found in plants, as described by Mounicou et al [25]. Thus, we can assume that Se ions may be cotransported by the same protein carriers with Cd ions, consequently reducing the transport of Cd into the cells [26].…”

Influence of Heavy Metals and Nutrient Concentrations on Selenium Geochemical Behavior in Soil-Rice System

“…In recent years, the interaction of Se and other elements (including nutrient elements like K, Ca, Mg, P, and Sm and heavy metals like Cd, Hg, and Cu) in the soil-plant system have been carried out. For example, Se-Hg antagonism may exist in the soil-rice system in this study, but there have been few studies investigating this putative Se-Hg antagonism in rice [42,43]. From these limited reports, the Se-Hg antagonism in rice may be primarily due to the formation of a high molecular weight Hg-Se-containing complex in plant roots.…”

Study on the protective role of selenium against cadmium toxicity in lactic acid bacteria: An advanced application of ICP-MS

“…Within this context, selenium has been classified as an antioxidant and/or a heavy metal antagonist [13]. The protective effect of selenium against mercury toxicity in different biological systems appears to have been the most studied [14][15][16][17][18][19]. Beneficial effects of selenium in exposure to cadmium and silver have also been observed and several studies focused the elucidation of mechanisms involved [17,[20][21][22][23] although a full mechanistic explanation has not been realized.…”