Soil selenium uptake and root system development in plant taxa differing in Se‐accumulating capability

Abstract

Summary• Phytoremediation of Se-contaminated soils and sediments may be more feasible if accumulating taxa are identified that can extract the more refractory forms of Se.• In a glasshouse study, the capacity of six plant genotypes to take up labile and nonlabile soil Se was evaluated by amending five high-Se soils (2 -21 mg kg − 1 total Se) with carrier-free 75 Se, and cropping them with Astragalus bisulcatus , Astragalus canadensis , Brassica juncea , Sporobolus airoides , and two ecotypes of Stanleya pinnata .• The biologically labile pool of soil Se ( L -value) was computed from the isotopic signature of the harvested shoots, and ranged from 2 to 37% of the total soil Se. The chemically labile pool ( E -value) was determined via extraction in 0.1 M KCl, and ranged from 4 to 73% of total soil Se. None of the plants tested yielded L -values that were consistently greater than the E -values, suggesting that all plants, including Se hyperaccumulators, access the same labile pools of Se.• Root-growth experiments in rhizoboxes using Se-enriched soil were also performed. Although our observations were not as striking as those made for the Zn(Cd)-accumulator Thlaspi caerulescens , the tendency for roots of some Seaccumulators to proliferate in soil where Se is present deserves further investigation.

Selenium in higher plants: understanding mechanisms for biofortification and phytoremediation

“…In another study, examination of Se accumulation by 16 populations of S. pinnata, an Se-hyperaccumulating species, found that shoot Se concentration can differ from 1.4 to 3.6-fold between populations [41]. Further studies revealed that both hyperaccumulators and nonaccumulators seem to access the same labile pools of Se in soil; therefore, Se-hyperaccumulators might be no better at accumulating Se from a relatively low-available-Se soil than are nonaccumulators, and root proliferation in Se-enriched soil (positive chemotaxis) might contribute to Se hyperaccumulation [42].…”

Molecular Mechanisms of Selenium Tolerance and Hyperaccumulation in Stanleya pinnata

“…Se hyperaccumulators do possess some unexplained physiological traits associated with growing on Se-enriched soils. S. pinnata roots have been reported to grow toward Se-rich soil in split-box experiments, and Astragalus species have been documented to grow slower and are smaller in the absence of Se in soils (Trelease and Trelease, 1938;Trelease and Beath 1949;Goodson et al, 2003).…”

Spatial Imaging, Speciation, and Quantification of Selenium in the Hyperaccumulator PlantsAstragalus bisulcatusandStanleya pinnata

“…Hyperaccumulator plants seek out and rapidly assimilate selenate (SeO 4 22 ) from the soil, preferentially over sulfate (SO 4 22 ; Bell et al, 1992). The roots of Se hyperaccumulators were found to grow preferentially toward SeO 4 22 -enriched soils, suggesting that elemental chemotaxis may exist in roots (Goodson et al, 2003). The mechanisms and reasons for the increased preferential uptake and sequestration of Se by these specialized plant species remain largely unknown (Sors et al, 2005b).…”