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The extensive use of rare earth elements (REEs) has increased their environmental levels. REE pollution concomitant with acid rain in many agricultural regions can affect crop growth. Cytosol free calcium ions (Ca 2+ ) play an important role in almost all cellular activities. However, no data have been reported regarding the role of cytosol free Ca 2+ in plant roots simultaneously exposed to REE and acid rain. In this study, the effects of exposures to lanthanum(III) and acid rain, independently and in combination, on cytosol free Ca 2+ levels, root activity, metal contents, biomass, cytosol pH and La contents in horseradish roots were investigated. The simultaneous exposures to La(III) and acid rain increased or decreased the cytosol free Ca 2+ levels, depending on the concentration of La(III), and these effects were more evident than independent exposure to La(III) or acid rain. In combined exposures, cytosol free Ca 2+ played an important role in the regulation of root activity, metal contents and biomass. These roles were closely related to La(III) dose, acid rain strength and treatment mode (independent exposure or simultaneous exposure). A low concentration of La(III) (20 mg L −1 ) could alleviate the adverse effects on the roots caused by acid rain, and the combined exposures at higher concentrations of La(III) and acid rain had synergic effects on the roots. [ABSTRACT FROM AUTHOR]

The environmental safety of rare earth elements (REEs), especially the toxic effect of REEs on plants, has attracted increasing attention. However, the cellular mechanism of this toxic effect remains largely unknown. Here, the toxic effects of heavy REE terbium ion [Tb(III)] on the cell membrane of horseradish roots were investigated by using electron microscope autoradiography (EMARG) and histochemical methods. The results indicated that Tb(III) was distributed in the extracellular and intracellular spaces of the roots after horseradish was treated with Tb(III). Moreover, the percentage contents of the unsaturated fatty acids in the membrane lipids, the current of the outward K + channel and the average diameter of membrane proteins in the roots of horseradish treated with Tb(III) were decreased; on the contrary, the percentage contents of the saturated fatty acids and malondialdehyde in the roots of horseradish treated with Tb(III) were increased. Furthermore, the contents of intracellular N, P, Mg and Fe in the roots of horseradish treated with Tb(III) were decreased, while the contents of intracellular K and Ca in the roots of horseradish treated with Tb(III) were increased. Finally, the effects of Tb(III) on horseradish roots were increased with increasing concentration or duration of Tb(III) treatment. In conclusion, after horseradish was treated with Tb(III), Tb(III) could enter the cells of horseradish roots and lead to the toxic effects on horseradish, which caused the oxidation of the unsaturated fatty acids in the membrane lipids, the changes in the membrane proteins (including the outward K + channel), the decrease in the membrane fluidity, and then the inhibition of the intracellular/extracellular-ion exchange in horseradish roots. [ABSTRACT FROM AUTHOR]

The wide application of rare earth elements (REEs) has led to the accumulation of REEs in soil and plant. Thereby, the effect of Tb3+ on the contents of cytosolic nutrient elements in horseradish was investigated with the synchronous detection technique of scanning electron microscope and energy dispersive X-ray spectrometry. It was found for the first time that the foliar spraying treatment of Tb3+ destroyed the structure of horseradish mesophyll cells, and then changed the contents of the cytosolic nutrient elements in horseradish, especially Ca. The effect of Tb3+ was increased with increasing the concentration of Tb3+. The hydroponical treatment of Tb3+ could not obviously change the structure of protoplast and the contents of the cytosolic nutrient elements in horseradish leaves. The results indicated that the accumulation of Tb3+ in soil and plant leaves displayed the different toxic effect on plant leaves. [Copyright &y& Elsevier]

Abstract: The physical immobilization behavior of horseradish peroxidase (HRP) on cellulosic fiber surfaces was characterized using adsorption and inactivation isotherms measured by the depletion method followed by fitting of Langmuir’s and Freundlich’s models to the experimental data. The adsorption and inactivation behavior of simpler and relatively non-porous high and low crystalline cellulosic substrates (microcrystalline cellulose and regenerated cellulose) as well as more complex and porous cellulosic pulp fibers (bleached kraft softwood fibers) were investigated. The effect of the sorbent surface energy on HRP adsorption was demonstrated by increasing the hydrophobicity of the cellulosic fibers using an internal sizing agent. The influence of the fiber surface charge density on HRP adsorption was studied via modification of the cellulosic fibers using TEMPO (2,2,6,6-tetramethyl-1-piperidiniloxy radical)-mediated oxidation methods. Results showed that hydrophobic interactions had a much larger effect on HRP adsorption than electrostatic interactions. More hydrophobic fiber surfaces (lower polar surface energy) result in larger enzyme-fiber binding affinity constants and higher binding heterogeneity. It was also found that oxidation of the cellulosic fiber substrate reduces enzyme adsorption affinity but significantly increases the loading capacity per unit weight of the surface. [Copyright &y& Elsevier]

Abstract: Polypyrrole was synthesized in high yield by a biocatalytic method in mild aqueous media using hydrogen peroxide as oxidizer. A redox mediator, 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) diammonium salt, was used to oxidize the pyrrole. ABTS is a very effective peroxidase substrate, which was enzymatically oxidized to generate a radical cation that in turn was able to chemically oxidize pyrrole. This indirect biocatalytic method was implemented because pyrrole is not a substrate of horseradish peroxidase, however, the polymerization process was successfully optimized and later adapted to prepare also polypyrrole thin films and water dispersible polypyrrole colloids. The polypyrrole powder and colloids were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, electrical conductivity, and thermogravimetric analysis. In addition, the deposition of the polypyrrole thin film was monitored using a quartz-crystal microbalance and its morphology studied by optical and scanning electron microscopy. The biocatalytic polymerization of pyrrole results in a polymer spectroscopically very similar to chemically synthesized polypyrrole. [Copyright &y& Elsevier]

Abstract: The agricultural application of rare-earth elements (REEs) would promote REEs inevitably to enter in the environment and then to threaten the environmental safety and human health. Therefore, the distribution of the REEs ion, 141Ce(III) and effects of La(III), Ce(III) and Tb(III) on the distribution of horseradish peroxidase (HRP) in horseradish mesophyll cells were investigated with electron microscopic radioautography and transmission electron microscopic cytochemistry. It was found for the first time that REEs ions can enter into the mesophyll cells, deposit in both extra and intra-cellular. Compared to the normal condition, after the horseradish leaves treated with La(III) or Tb(III), HRP located on the tonoplast is decreased and HRP is mainly located on the cell wall, while HRP is mainly located on the plasma membrane after the horseradish leaves were treated with Ce(III). This also indicated that REEs ions may regulate the plant growth through changing the distribution of enzymes. [Copyright &y& Elsevier]