Selenium in Soil Inhibits Mercury Uptake and Translocation in Rice (Oryza sativa L.)

Abstract

A great number of studies have confirmed that mercury-selenium (Hg-Se) antagonism is a widespread phenomenon in microorganisms, fish, poultry, humans, and other mammals. However, by comparison, little attention has been paid to plants. To investigate the influence of Se on the uptake and translocation of methylHg/inorganic Hg (MeHg/IHg) in the rice-soil system, we determined the levels of Se, IHg, and MeHg in different parts of rice plants (including the root, stem, leaf, husk, and grain (brown rice)) and corresponding soils of root zones collected from a Hg mined area, where Hg and Se co-occur due to historic Hg mining and retorting activities. The results showed that, in general, the Se levels were inversely related to the levels of both IHg and MeHg in the grains. In addition, a consistent reduction in translocation of both IHg and MeHg in the aerial shoots (i.e., the stem, leaf, husk, and grain) with increasing Se levels in the soils was observed. Furthermore, the Se levels were positively correlated with the IHg levels in the soils and the roots. These results suggest that Se may play an important role in limiting the bioaccessibility, absorption, and translocation/bioaccumulation of both IHg and MeHg in the aerial rice plant, which may be related to the formation of an Hg-Se insoluble complex in the rhizospheres and/or roots.

Retrospective study of methylmercury and other metal(loid)s in Madagascar unpolished rice (Oryza sativa L.)

“…An inverse relationship between Hg species and Se was previously observed in rice grain (e.g., Zhang et al, 2012) as well as fish tissue (Peterson et al, 2009), while the trend was inverse but weak for this data set (p>0.05, Table 4). In rice grain, an inverse relationship between Hg species and Se may reflect competition for thiols in phloem.…”

“…This is a retrospective study of archived rice germplasm, and other matrices (e.g., paddy soil or irrigation water) were not available. Other researchers reported a strong positive correlation between rice THg and MeHg concentrations for rice cultivated in China, California, USA and Cambodia (Rothenberg et al, 2014), while an inverse correlation was observed between rice Hg species and Se (Zhang et al, 2012). We hypothesize interactions will be similar among these Madagascar rice varieties.…”

“…Metal(loid)s are often studied in isolation; however, chemical similarities, competition for ligands, and plant-soil interactions may alter rice grain content (e.g., Impa and Johnson-Beebout, 2012; Li et al, 2012; Williams et al, 2009a; Zhang et al, 2012). In addition, some trace elements are nutritious (e.g., Zn and Se) while others are toxic (e.g., As and Cd), making it difficult to assess the nutritional quality of rice grain without considering both.…”

Incorporation of Decomposed Crop Straw Affects Potential Phytoavailability of Mercury in a Mining-Contaminated Farming Soil

“…For Hg T analysis, soil samples were digested in a water bath (95°C) using concentrated HCl and HNO 3 (1:3, v/v; Meng et al 2010;Zhang et al 2012). Concentrations of Hg T in the digestion or extraction solutions were measured using a DMA-80 direct mercury analyzer (Milestone, Italy) based on EPA Method 7473.…”

The Effect of Selenium on Mercury Transport Along the Food Chain

“…One possibility is to reduce the uptake of Hg by plants as well to reduce the bioavailability of Hg in plants to consumers. In the last decades several studies showed the antagonistic action of Se in soil on the uptake and translocation of Hg in plants (Shanker et al, 1996a,b;Thangavel et al, 1999;Mounicou et al, 2006;Zhang et al, 2012). Mercury has a high affinity to bind with Se and form insoluble mercury selenides, whichcan prevent negative effects of mercury in animals (rev in Raymond et al 2004).…”