Reduced phytotoxicity of propazine on wheat, maize and rapeseed by salicylic acid.

Propazine belongs to the triazine herbicide family and widely used in the farmland for crop production. Recent studies have shown that the residue of propazine in environment is accumulative. This inevitably results in accumulation of propazine in crops. Therefore, reduction of propazine toxicity and accumulation in crops is critically important. In this study, the growth of wheat, maize and rapeseed was significantly inhibited by 2, 8 and 0.4 mg kg-1 propazine in soils. The chlorophyll content of the three crops also showed significant decrease, while the electrolyte permeability, a biomarker of cellular damage, increased in the plant cells. However, when plants were sprayed with 5 mg L-1 of salicylic acid (SA), the propazine phytotoxicity of the crops was relieved, with increased chlorophyll content and reduced electrolyte permeability of all crops. Meanwhile, the activities of peroxidase (POD) and glutathione transferase (GST) remained lower. The propazine accumulation in the crops and the residues in the soil were determined by high performance liquid chromatography. The concentration of propazine in plants and soils treated by SA was less than that of the untreated control. Six propazine degraded products (derivatives) in rhizosphere of wheat were characterized using ultraperformance liquid chromatography with a quadrupole-time-of-flight tandem mass spectrometer. Our work indicates that the improved growth of crops was possibly due to the acceleration of propazine degradation by salicylic acid.

Detoxification of Atrazine by Low Molecular Weight Thiols in Alfalfa (Medicago sativa).

Low molecular weight (LMW) thiols in higher plants are a group of sulfur-rich nonprotein compounds and play primary and multiple roles in cellular redox homeostasis, enzyme activities, and xenobiotics detoxification. This study focused on identifying thiols-related protein genes from the legume alfalfa exposed to the herbicide atrazine (ATZ) residues in environment. Using high-throughput RNA-sequencing, a set of ATZ-responsive thiols-related protein genes highly up-regulated and differentially expressed in alfalfa was identified. Most of the differentially expressed genes (DEGs) were involved in regulation of biotic and abiotic stress responses. By analyzing the genes involved in thiols-mediated redox homeostasis, we found that many of them were thiols-synthetic enzymes such as γ-glutamylcysteine synthase (γECS), homoglutathione synthetase (hGSHS), and glutathione synthetase (GSHS). Using liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS), we further characterized a group of ATZ-thiols conjugates, which are the detoxified forms of ATZ in plants. Cysteine S-conjugate ATZ-HCl+Cys was the most important metabolite detected by MS. Several other ATZ-conjugates were also examined as ATZ-detoxified metabolites. Such results were validated by characterizing their analogs in rice. Our data showed that some conjugates under ATZ stress were detected in both plants, indicating that some detoxified mechanisms and pathways can be shared by the two plant species. Overall, these results indicate that LMW thiols play critical roles in detoxification of ATZ in the plants.

A newly developed molecularly imprinted polymer on the surface of TiO2 for selective extraction of triazine herbicides residues in maize, water, and soil.

A new surface molecularly imprinted polymer (MIP) based on nano-TiO2 was developed using propazine (Pro) as a template molecule, ethyleneglycol dimethacrylate (EGDMA) as a crosslinker, methacrylic acid (MAA) as a functional monomer, and 2,2'-azobis (isobutyronitrile) (AIBN) as an initiator. Structures of the newly synthesized surface MIPs were characterized by Fourier transmission infrared spectrometry (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD). The MIP had a good adsorption capacity and high recognition selectivity to propazine. Meanwhile, it exhibited a cross-selectivity for simazine (Sim) and atrazine (Atr). The MIPs were used as a solid phase extraction (SPE) material. Concomitant extraction, purification, and determination of three pesticides (Pro, Sim, and Atr) residues in water, soil, and maize plant and grain samples were performed by MIP-SPE coupled with high performance liquid chromatography (HPLC). The highly selective separation and enrichment of Pro, Atr, and Sim from the complex environmental media can be achieved. Thus, the newly developed technique provides an analytical platform to quantify the trace amount of Pro, Sim, and Atr residues in multi environmental media and food source.

Core-shell magnetic molecularly imprinted polymers as sorbent for sulfonylurea herbicide residues.

Sulfonylurea herbicides are widely used at lower dosage for controlling broad-leaf weeds and some grasses in cereals and economic crops. It is important to develop a highly efficient and selective pretreatment method for analyzing sulfonylurea herbicide residues in environments and samples from agricultural products based on magnetic molecularly imprinted polymers (MIPs). The MIPs were prepared by a surface molecular imprinting technique especially using the vinyl-modified Fe3O4@SiO2 nanoparticle as the supporting matrix, bensulfuron-methyl (BSM) as the template molecule, methacrylic acid (MAA) as a functional monomer, trimethylolpropane trimethacrylate (TRIM) as a cross-linker, and azodiisobutyronitrile (AIBN) as an initiator. The MIPs show high affinity, recognition specificity, fast mass transfer rate, and efficient adsorption performance toward BSM with the adsorption capacity reaching up to 37.32 mg g(-1). Furthermore, the MIPs also showed cross-selectivity for herbicides triasulfuron (TS), prosulfuron (PS), and pyrazosulfuron-ethyl (PSE). The MIP solid phase extraction (SPE) column was easier to operate, regenerate, and retrieve compared to those of C18 SPE column. The developed method showed highly selective separation and enrichment of sulfonylurea herbicide residues, which enable its application in the pretreatment of multisulfonylurea herbicide residues.