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Wu Z.,Guangdong Academy of Agricultural Sciences | Wu Z.,Key Laboratory of Testing and Evaluation for Agro product Safety and Quality | Wu Z.,Laboratory of Quality and Safety Risk Assessment for Agro product Guangzhou | Wang F.,Guangdong Academy of Agricultural Sciences | And 21 more authors.
Environmental and Experimental Botany | Year: 2016

Silicon (Si) and selenium (Se) are generally considered as beneficial elements for the growth of higher plants, especially for those grown in heavy-metal stressed environments. However, the mechanisms underlying the roles of Si and Se in mitigating cadmium (Cd) stress in flowering Chinese cabbage (Brassica campestris L. ssp. chinensis var. utilis) are still poorly understood. Here, we investigated the comparative responses to Si and Se in relation to Cd uptake, compartmentation in roots, and xylem transport in flowering Chinese cabbage plants under Cd stress. Addition of Si or/and Se efficaciously alleviated the toxicity of Cd as demonstrated by increasing of tissue (shoots and roots) biomass of plants exposed to high Cd stress, especially for their coupling treatments with high doses. In compare with the Cd-alone treatment, the application of Si alone or in combination with Se greatly decreased plant shoot Cd concentrations as well as its translocation factor (TF), though the Cd concentrations in roots and the total Cd accumulation of whole plants showed increasing trends (especially for the treatments of high Si or coupling with Se), while no marked differences were found in plants exposed to the Se-alone treatment. Additionally, the application of Si alone or in combination with Se considerably reduced the Cd concentrations and its proportions in symplast and apoplast root saps and increased them in cell wall fragments, while little changes were observed for the Se-alone treatment. Furthermore, a greatly decreased tendency was also displayed for the Cd concentrations in xylem saps exposed to the treatments containing Si alone or in combination with Se. Overall, our results reveal that Si-mediated alleviation of Cd toxicity may be due to decreasing Cd concentrations and its proportions in symplasts and apoplasts, enhancing adsorption of Cd on cell walls, and restriction root-to-shoot Cd translocation. However, Se mitigation may involve other mechanisms. © 2016 Elsevier B.V.


Huang J.X.,Guangdong Academy of Agricultural Sciences | Huang J.X.,Key Laboratory of Testing and Evaluation for Agro product Quality and Safety | Huang J.X.,Laboratory of Quality and Safety Risk Assessment for Agro product Guangzhou | Liu C.Y.,Guangdong Academy of Agricultural Sciences | And 14 more authors.
Environmental Monitoring and Assessment | Year: 2015

A simple and rapid method based on high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) was developed for the simultaneous determination of imidacloprid and chlorfenapyr residues in chieh-qua. Field trials were designed to investigate the dissipation and terminal residue behavior of the mixed formulation of imidacloprid and chlorfenapyr in chieh-qua in Guangzhou and Nanning areas. Risk assessment was performed by calculating the risk quotient (RQ) values. The developed analytical method exhibited recoveries of 89.9–110.3 % with relative standard deviations (RSDs) of 2.8–12.5 % at the spiked levels of 0.01, 0.10, and 1.00 mg/kg. The limit of detection (LOD) was 0.003 mg/kg, and the limit of quantification (LOQ) was 0.01 mg/kg for both imidacloprid and chlorfenapyr. It was found that the half-lives of imidacloprid in chieh-qua under field conditions were 3.3 and 3.5 days in Guangzhou and Nanning at a dose of 180 g ai/ha, while the half-lives of chlorfenapyr were 3.3 and 2.6 days, respectively. The terminal residues of imidacloprid and chlorfenapyr were from 0.01 to 0.21 mg/kg and from 0.01 to 0.46 mg/kg, respectively. Results of dietary exposure assessment showed that the RQ values were much lower than 1, indicating that the risk of imidacloprid and chlorfenapyr applied in chieh-qua was negligible to human health under recommended dosage and good agricultural practices. The proposed study would provide guidance for safe and reasonable use of imidacloprid and chlorfenapyr in chieh-qua cultivation in China. © 2015, Springer International Publishing Switzerland.

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