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Utilizing reliable and accurate positioning and navigation systems is crucial for saving the lives of rescue personnel and accelerating rescue operations. However, Global Navigation Satellite Systems (GNSSs), such as GPS, may not provide stable signals in dense forests. Therefore, integrating multiple sensors like GPS and Inertial Measurement Units (IMUs) becomes essential to enhance the availability and accuracy of positioning systems. To accurately estimate rescuers' positions, this paper employs the Adaptive Unscented Kalman Filter (AUKF) algorithm with measurement noise variance matrix adaptation, integrating IMU and GPS data alongside barometric altitude measurements for precise three-dimensional positioning in complex environments. The AUKF enhances estimation robustness through the adaptive adjustment of the measurement noise variance matrix, particularly excelling when GPS signals are interrupted. This study conducted tests on two-dimensional and three-dimensional road scenarios in forest environments, confirming that the AUKF-algorithm-based integrated navigation system outperforms the traditional Extended Kalman Filter (EKF), Unscented Kalman Filter (UKF), and Adaptive Extended Kalman Filter (AEKF) in emergency rescue applications. The tests further evaluated the system's navigation performance on rugged roads and during GPS signal interruptions. The results demonstrate that the system achieves higher positioning accuracy on rugged forest roads, notably reducing errors by 18.32% in the north direction, 8.51% in the up direction, and 3.85% in the east direction compared to the EKF. Furthermore, the system exhibits good adaptability during GPS signal interruptions, ensuring continuous and accurate personnel positioning during rescue operations.
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Laizhou Bay, a major breeding ground for economic marine organisms in the northern waters of China, is facing rapid environmental degradation. In this study, field surveys in this area were conducted in the spring, summer, and autumn of 2020. Microscopic observation and RuBisCO large subunit (rbcL) gene analysis were employed to understand the community structure and temporal dynamics of phytoplankton. The phytoplankton community structures detected by the two methods showed significant differences. Microscopic observation revealed the dominance of dinoflagellates in spring that shifted to the dominance of diatoms in summer and autumn. However, rbcL gene sequencing consistently identified diatoms as dominant throughout all three seasons, with their relative abundance showing an increasing trend. Conversely, the relative abundance of the second- and third-most abundant taxa, namely, haptophytes and ochrophytes, decreased as the seasons transitioned. rbcL gene sequencing annotated more species than microscopy. It could detect haptophytes and cryptophytes, which were overlooked by microscopy. In addition, rbcL gene sequencing detected a remarkable amount of Thalassiosira profunda, which was previously unidentified in this sea area. However, it appeared to underestimate the contribution of dinoflagellates considerably, with most taxa being only identified through microscopic identification. The two methods jointly identified 28 harmful algal bloom taxa with similar detection quantities but substantial differences in species composition. Phytoplankton communities were influenced by temperature, salinity, and nutrients. The results of this work suggest that a combination of multiple techniques is necessary for a comprehensive understanding of phytoplankton.
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The multiferroic rare-earth-substituted BiFeO_{3} has emerged as a promising candidate to achieve ultralow-energy-dissipation logic or memory devices, but the fundamental details of the switching mechanism involving the electrical, structural, and magnetic degrees of freedom is not fully understood, in particular, in its single-phase form. Here, a first-principles-based computational scheme is used to study Nd-doped BiFeO_{3} as a model system. The structure that yields a reduced P-E hysteresis loop is found to be ferrielectric with modulated octahedral tiltings, and it is shown that both the in-plane and out-of-plane ferromagnetization can be controlled by an applied electric field. The switching behaviors can be well interpreted by a Landau-type model, in which the magnetoelectric coupling is indirect and mediated by octahedral tiltings. The effects of varied composition and temperature are further discussed, revealing important correlations between the polarization switching and the robustness of the control of magnetization.
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Pd/Cu-catalyzed cascade Heck-type reactions of alkenyl halides with terminal alkynes have been developed. This research provides an efficient atom-economical approach to access a variety of highly substituted pyrrolidines in moderate to good yields. This protocol features readily available substrates, broad substrate scope, easy scale-up, high selectivities and versatile transformations.
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OBJECTIVE: To evaluate thyroid-stimulating immunoglobulin (TSI) and thyrotropin receptor antibodies (TRAb) diagnostic performance for Graves' disease (GD) and determine clinical cut-off value for diagnosing GD. METHODS: Of 1369 retrospectively enrolled subjects, 1364 had a definitive diagnosis of untreated GD (GD-UT, n = 87); treated GD (GD-T, n = 206); autoimmune thyroid disease (AIT, n = 241); thyroid nodules (TN, n = 677); subacute thyroiditis (ST, n = 28); healthy subjects (HS, n = 125); other diseases with serological hyperthyroidism (n = 5) and were grouped into the following: UT-GD and control groups (AIT, TN, ST, and HS); and UT-GD and non-GD hyperthyroidism groups. Diagnostic performance of TSI and TRAb was evaluated using area under the curve (AUC) of receiver-operating characteristic (ROC) curve, and optimal clinical cut-off value was determined using maximization of Youden index. RESULTS: TRAb AUC and clinical cut-off value for diagnosing GD were 0.981 and 1.245 IU/L (sensitivity, 96.6%; specificity, 97.1%; positive predictive value [PPV], 71.8%; negative predictive value [NPV], 99.9%; positive likelihood ratio [PLR], 33.31; negative likelihood ratio [NLR, 0.035), respectively, for the GD-UT and control groups. Those for TSI were 0.992 and 0.467 IU/L (sensitivity 98.8%; specificity, 96.4%; PPV, 68.8%; NPV, 99.9%; PLR, 27.472; NLR, 0.011). Those for TRAb in GD-UT and non-GD hyperthyroidism groups were 0.923 and 1.78 IU/L (sensitivity, 92.0%; specificity, 89.1%; PPV, 93%; NPV, 87.5%; PLR, 8.44; NLR, 0.089), respectively. For TSI, these were 0.92 and 0.545 IU/L (sensitivity, 97.7%; specificity, 83.6%; PPV, 90.4%; NPV, 95.8%; PLR27.472, NLR, 0.011), respectively. CONCLUSION: TSI diagnostic performance for GD was excellent and had better sensitivity than TRAb.
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Doença de Graves , Hipertireoidismo , Humanos , Doença de Graves/diagnóstico , Doença de Graves/terapia , Hipertireoidismo/diagnóstico , Hipertireoidismo/terapia , Imunoglobulinas Estimuladoras da Glândula Tireoide , Estimulador Tireóideo de Ação Prolongada/uso terapêutico , Receptores da Tireotropina , Estudos Retrospectivos , TireotropinaRESUMO
The palladium-catalyzed asymmetric carboamination reaction is one of the most significant transformations in organic chemistry. Herein, we report the first palladium-catalyzed asymmetric alleneamination of ß,γ-unsaturated hydrazones with propargylic acetates. This protocol enables the efficient installation of various multisubstituted allene groups onto dihydropyrazoles in good yields with excellent enantioselectivities. The chiral sulfinamide phosphine ligand Xu-5 exhibits highly efficient stereoselective control in this protocol. The salient features of this reaction include the readily available starting materials, a broad substrate scope, an easy scale-up, mild reaction conditions and versatile transformations.
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BACKGROUND: Triazole resistance in the human fungal pathogen Aspergillus fumigatus has been a growing challenge in clinic treatment with triazole drugs such as itraconazole. The fast evolvement of triazole resistance in A. fumigatus in the ecosystem has drawn great attention, and there has been a possible link between the application of triazole fungicides in agriculture and triazole resistance in A. fumigatus. The change in susceptibility of A. fumigatus exposed to the new chiral triazole fungicide mefentrifluconazole was investigated in this study. RESULTS: The results indicated that triazole resistance in A. fumigatus was acquired with exposure to mefentrifluconazole at a level of greater than or equal to 2 mg L-1 in liquid medium and soil (not at 0.4 nor 1 mg L-1 ). Interestingly, stereoselectivity was found in the acquisition of triazole resistance in A. fumigatus when exposed to mefentrifluconazole. R-mefentrifluconazole, which is very active on plant pathogens, exhibited stronger possibility in the development of the resistance in A. fumigatus than its antipode. Overexpression of cyp51A, AtrF, AfuMDR1 and AfuMDR4 were associated with the acquired resistance in A. fumigatus with hereditary stability. CONCLUSION: The results suggest that triazole resistance in A. fumigatus could be resulted from the selection of mefentrifluconazole at concentrations larger than 2 mg L-1 . Mefentrifluconazole should be applied within the dosage recommended by good agricultural practice to avoid the resistance in A. fumigatus in soil. This also may be applicable to other triazole fungicides. © 2022 Society of Chemical Industry.
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Aspergillus fumigatus , Farmacorresistência Fúngica , Fungicidas Industriais , Triazóis , Humanos , Antifúngicos/farmacologia , Aspergillus fumigatus/efeitos dos fármacos , Aspergillus fumigatus/genética , Farmacorresistência Fúngica/genética , Ecossistema , Proteínas Fúngicas/genética , Fungicidas Industriais/farmacologia , Testes de Sensibilidade Microbiana , Solo , Triazóis/farmacologiaRESUMO
Purpose: Human follicular fluid (FF) is a complex biological fluid that contributes to the micro-environment of oocyte development. The aim of this study was to evaluate the role of steroid and gonadotropic hormones levels and mitochondrial function in embryo development during in vitro fertilization cycles. Methods: This was a cohort study of 138 women receiving IVF/ICSI, including 136 FF samples from 109 infertile women. FF steroid and gonadotropic hormones levels were tested by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and immunoassays. The mRNA expression levels of mitochondrial electron transport chain (ETC) complex genes from FF exosomes were detected by qPCR. Results: Analysis of these individual FF concentrations revealed that LH and FSH concentrations were higher in follicles in which the oocyte developed into a top quality (TQ) blastocyst (LH: 9.44 ± 2.32mIU/ml, FSH: 9.32 ± 1.01mIU/ml) than those in which there was a failure of fertilization (LH: 5.30 ± 0.84mIU/ml, FSH: 6.91 ± 0.62mIU/ml). In contrast, follicular cortisone concentrations were lower for oocytes that resulted in a TQ blastocyst (12.20 ± 0.82mIU/ml). The receiver operating characteristic analysis showed that FF LH and FSH levels predicted TQ blastocyst with excellent AUC value of 0.711 and 0.747. Mitochondrial ETC complex I and III mRNA levels were increased in the FF exosomes of TQ blastocyst. Correlation analysis showed that mRNA levels of ETC complex I was positively correlated with LH and FSH levels in FF. Conclusion: The levels of FF steroid and gonadotropic hormones from single follicle can predetermine subsequent embryo development to some extent. Furthermore, impaired exosome mitochondrial dysfunction is a potiential event that causes hormone change in embryo development.
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Exossomos , Infertilidade Feminina , Gravidez , Feminino , Humanos , Líquido Folicular/metabolismo , Infertilidade Feminina/metabolismo , Exossomos/metabolismo , Estudos de Coortes , Cromatografia Líquida , Espectrometria de Massas em Tandem , Desenvolvimento Embrionário , Gonadotropinas/metabolismo , Esteroides , Hormônio Foliculoestimulante/metabolismo , Mitocôndrias/metabolismo , RNA Mensageiro/metabolismoRESUMO
Introducing suitable interfacial chemical bonds into heterojunctions can increase the charge carrier density, propel the charge separation, and facilitate interfacial charge extraction in photoanodes for photoelectrochemical (PEC) water oxidation. However, tuning chemical bonds at heterojunction interfaces and elucidating their influences on band alignment and the associated evolution of PEC performance remain elusive. Herein, Bi-S bonds were introduced into the interface of a CdIn2S4 (CIS)/Bi2WO6 (BWO) heterojunction. In situ irradiated X-ray photoelectron spectroscopy and electron spin resonance signals confirm that the Bi-S bond transforms the band alignment from type II to the direct Z-scheme, significantly enhancing the carrier separation efficiency. Theoretical calculations show that the Bi-S bond not only acts as an atomic-level charge transfer channel, but also changes the migration pathway and distance within the heterojunction. As a result, the optimized CIS/BWO photoanode exhibits a relatively high PEC performance of 4.25 mA cm-2 at 1.23 V vs. RHE (VRHE) and a low onset potential of 0.30 VRHE. This work presents a new avenue to construct comprehensively improved photoanodes by tuning the interfacial structures at the atomic level.
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Although azoxystrobin has been widely applied on various crops, little is known about the bioavailability of azoxystrobin in the soil-vegetable system. In this study, the uptake, accumulation and translocation of azoxystrobin as affected by soil characteristics and plant species were respectively investigated. The accumulation amount of azoxystrobin in pakchoi increased as soil adsorption decreased and was positively associated with its concentration in pore water (Cpw), which was mainly affected by soil organic matter content. Therefore, Cpw could be a candidate for the estimation of azoxystrobin accumulation in pakchoi. In all the tested vegetables, azoxystrobin was mainly accumulated in roots, and its upward translocation was limited. Root lipid content was a major factor affecting the uptake and translocation of azoxystrobin in different vegetables.
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Poluentes do Solo , Solo , Produtos Agrícolas , Pirimidinas , Poluentes do Solo/análise , Estrobilurinas , VerdurasRESUMO
Cannabidiol (CBD) has poor water solubility and is subjected to extensive first-pass metabolism. These absorption obstacles are responsible for low and variable oral bioavailability of CBD. This study endeavored to improve CBD bioavailability by intramuscular (IM) injection of CBD nanocrystals (CBD-NC). The nanocrystals were prepared by antisolvent precipitation method and were characterized in terms of the particle size, polydispersity index (PDI), zeta potential, morphology, and crystalline status. CBD-NC displayed a particle size of 141.7±1.5 nm, a PDI of 0.18±0.01, and a zeta potential of -25.73 mV. CBD-NC freeze-dried powder using bovine serum albumin (BSA) as cryoprotectant had good redispersibility, and the average particle size was 139.1±1.4 nm after reconstitution. Moreover, these freeze-dried powders were characterized for drug loading and pH and were evaluated for in vitro dissolution and in vivo studies in a rat model. The in vivo results showed that AUC0-24 h and Cmax of CBD by IM injection of CBD nanocrystals increased significantly compared with that of oral (P.O) administration of CBD nanocrystals and CBD oil solution. This underlines the nano-sized CBD could be suggested as a practical and simple nanosystem for IM delivery with improved bioavailability. More importantly, these results pave the way for future development of CBD-NC retentive dosage forms. Graphical abstract.
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Canabidiol , Nanopartículas , Animais , Disponibilidade Biológica , Nanopartículas/química , Tamanho da Partícula , Ratos , SolubilidadeRESUMO
Elaborating the environmental behavior of mefentrifluconazole, a novel triazole fungicide, in stereoselective level is of paramount importance for the application of the pesticide in agriculture. In this study, the enantioselective bioactivity, acute toxicity and stereoselective bioaccumulation of mefentrifluconazole in earthworm (Eisenia fetida) were investigated. Bioactivity tests against four pathogens revealed that R-(-)-mefentrifluconazole exhibited approximately 11-113 times higher bioactivity than its S-(+)-mefentrifluconazole. However, the LC50 of S-(+)-, rac- and R-(-)-mefentrifluconazole to earthworm was measured to be 4.1, 11.4 and 7.3 µg/cm2, respectively, indicating active ingredient R-(-)-mefentrifluconazole is less toxic than its racemate and S-form. Accumulation of mefentrifluconazole in earthworms was non-enantioselective and negatively related to its adsorption onto soils. The concentration of mefentrifluconazole in in situ pore water (CIPW) and CaCl2 extraction (CCaCl2) was closely related to its accumulation in earthworms, suggesting that CIPW and CCaCl2 could be appropriate indicators for estimation of the bioavailability of mefentrifluconazole in soil. Conclusively, our study provides necessary information for the risk assessment of mefentrifluconazole in agriculture.
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Fungicidas Industriais , Oligoquetos , Poluentes do Solo , Animais , Bioacumulação , Fluconazol/análogos & derivados , Fungicidas Industriais/análise , Fungicidas Industriais/toxicidade , Solo , Poluentes do Solo/análise , Poluentes do Solo/toxicidade , Estereoisomerismo , Triazóis/análise , Triazóis/toxicidadeRESUMO
Residual injury of atrazine to the succeeding crops has been frequently reported. It is necessary to find a solution for the detoxification of atrazine contaminated soil. A high-efficient bacterial strain Arthrobacter sp. C2 for atrazine degradation was isolated in this study. The genomic information of the isolate C2, and its degradation characteristics and potential application in detoxification of atrazine contaminated soil were investigated. The results indicated that the isolate C2 genome contained 4,305,216 bp nucleotides, three plasmids, and 4705 coding genes. The degradation rates of atrazine at levels of 1, 10, 100 mg/L by the isolate C2 were 0.34, 1.94, 18.64 mg/L/d, respectively. The optimum temperature and pH for the isolate C2 to degrade atrazine were 30 °C and 7.0-9.0. Based on the metabolites detected by UPLC-TOF-MS/MS and genome annotation of the isolate C2, a common metabolic pathway of atrazine was proposed as that atrazine is firstly dechlorinated into hydroxyatrazine, and subsequently to N-isopropylammelide via dealkylation, and ultimately deaminated to cyanuric acid. Introduction of the isolate C2 into soil can enhance degradation of atrazine and thus eliminate the toxic effect of this herbicide on wheat growth. Our results indicate that the strain C2 could be a potential bioresource for bioremediation of atrazine contaminated soil.
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Arthrobacter , Atrazina , Herbicidas , Poluentes do Solo , Arthrobacter/genética , Atrazina/análise , Atrazina/toxicidade , Biodegradação Ambiental , Herbicidas/análise , Herbicidas/toxicidade , Microbiologia do Solo , Poluentes do Solo/análise , Espectrometria de Massas em TandemRESUMO
Residual pesticides in soil may be taken up by crops and negatively affect food safety. The uptake mechanism of imidacloprid and propiconazole was studied using wheat roots. The factors affecting root uptake were also studied with different crops and in different soils. Imidacloprid and propiconazole were taken up by wheat roots mainly through the symplastic and apoplastic pathways, respectively. Root protein and lipid contents were the main factors affecting the uptake and accumulation of imidacloprid and propiconazole by different crop roots, respectively. The uptake of imidacloprid and propiconazole in soil by wheat plants was linearly correlated with their concentrations in soil pore water, which were governed by soil characteristics. These results are helpful for understanding and estimating crop uptake of residual pesticides in soils.
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Produtos Agrícolas/metabolismo , Neonicotinoides/metabolismo , Nitrocompostos/metabolismo , Raízes de Plantas/metabolismo , Poluentes do Solo/metabolismo , Solo/química , Triazóis/metabolismo , Produtos Agrícolas/química , Neonicotinoides/química , Nitrocompostos/química , Raízes de Plantas/química , Triazóis/química , Triticum/química , Triticum/metabolismoRESUMO
A total of 191 soil samples from Hangzhou, China, were submitted to detect non-wild-type (non-WT) Aspergillus fumigatus and its associated mechanisms. There were 2 (4.7%), 13 (12.4%), and 31 (23.1%) isolates identified as non-WT in 2014, 2016, and 2018, respectively. The resistant mutations of TR34/L98H, TR46/Y121F/T289A, and TR34/L98H/S297T/F495I were found in 3, 5, and 5 non-WT isolates. The G448S mutation, previously only found in clinical settings, was detected in A. fumigatus from soil samples.
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Aspergillus fumigatus , Farmacorresistência Fúngica , Antifúngicos/farmacologia , Aspergillus fumigatus/genética , Azóis/farmacologia , China , Farmacorresistência Fúngica/genética , Proteínas Fúngicas/genética , Testes de Sensibilidade MicrobianaRESUMO
Aspergillus fumigatus is the primary agent of invasive aspergillosis (IA) causing high morbidity and mortality in immunocompromised patients. Triazole resistance in A. fumigatus and its sources have gained wide attention. For several years, environmental fungicides use has been proposed as the major cause for triazole resistance in A. fumigatus. However, there are few studies on azole-resistant A. fumigatus (ARAF) selected by triazole fungicides in agricultural systems. We studied the possible emergence of ARAF in the field after exposure to triazole fungicide tebuconazole. Our results showed that exposure to tebuconazole in soil selects for resistance to triazoles in A. fumigatus. The probability of ARAF developing in soils depends upon the concentrations of tebuconazole after application. We suggest that tebuconazole applications should be minimized to reduce selective pressure for the generation of ARAFs.
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Aspergillus fumigatus/efeitos dos fármacos , Farmacorresistência Fúngica/efeitos dos fármacos , Antifúngicos , Humanos , Testes de Sensibilidade Microbiana , Solo , Triazóis/farmacologiaRESUMO
Triazole-resistance in Aspergillus fumigatus is widespread. We evaluated whether triazole-resistance in A. fumigatus and its related cyp51A mutations, induced by a combination of the triazole fungicides difenoconazole and propiconazole, differs from resistance induced by the individual fungicides. Both difenoconazole and propiconazole can induce triazole-resistance in A. fumigatus. Resistance is much easier induced by formulated fungicides or a combination of these two fungicides compared with standard fungicides or individual fungicides, respectively. Six different mutations (G138S, G138D, H147Y, I246M, M263I and D430N) were identified in the induced resistant strains. The H147Y, I246M and M263I mutations were associated with triazole-resistance. This implies that the application of a combination of difenoconazole and propiconazole may result in higher triazole-resistance in A. fumigatus and more mutations in the cyp51A gene.
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Aspergillus fumigatus , Fungicidas Industriais , Antifúngicos/farmacologia , Aspergillus fumigatus/genética , Sistema Enzimático do Citocromo P-450/genética , Dioxolanos , Farmacorresistência Fúngica/genética , Proteínas Fúngicas/genética , Fungicidas Industriais/farmacologia , Mutação , Triazóis/farmacologiaRESUMO
Root uptake, translocation, and subcellular distribution of six pesticides (dinotefuran, thiamethoxam, imidacloprid, imazethapyr, propiconazole, and chlorpyrifos) with Kow ranging from -0.549 to 4.7 were investigated in wheat to study transportation and accumulation of pesticides. The root bioconcentration factor (RCF) of pesticides decreased with water solubility (R2 = 0.6121) and increased with hydrophobicity (when the pH-adjusted log Kow > 2, R2 = 0.925), respectively. The translocation of neutral pesticides from roots to shoots increased positively with water solubility (R2 > 0.6484) but decreased with hydrophobicity (R2 > 0.8039). The subcellular fraction concentration factor (SFCF) increased linearly with hydrophobicity of the tested pesticides (R2 > 0.958). The log RCF was positively correlated with log SFCF in root cell walls (R2 = 0.9894) and organelles (R2 = 0.9786). Transportation of the pesticides from roots to stems and stems to leaves was adversely affected by the log SFCF of cell walls and organelles of roots (R2 > 0.7997) and stems (R2 > 0.6666), respectively. Hydrophobicity-dependent SFCF is a factor governing accumulation of pesticides in roots after uptake and their subsequent upward translocation.
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Praguicidas/farmacocinética , Triticum/efeitos dos fármacos , Triticum/metabolismo , Transporte Biológico , Parede Celular/efeitos dos fármacos , Parede Celular/metabolismo , Interações Hidrofóbicas e Hidrofílicas , Praguicidas/química , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/metabolismo , Raízes de Plantas/efeitos dos fármacos , Raízes de Plantas/metabolismo , Brotos de Planta/efeitos dos fármacos , Brotos de Planta/metabolismo , Solubilidade , Triticum/citologia , Triticum/crescimento & desenvolvimentoRESUMO
Residual acetochlor and atrazine in soils, resulting from their extensive application to maize plants, may affect product safety of the ultimate wheat crop. To determine the potential uptake and accumulation of acetochlor and atrazine by wheat plants, the uptake mechanism, translocation, and subcellular distribution of these two herbicides were studied through hydroponic experiments (10 mg L-1). The results indicated that acetochlor can be taken up through the apoplastic pathway and can accumulate in wheat roots with little upward translocation. However, atrazine could be taken up by roots through the symplastic pathway and subsequently transported to the stems and leaves. Little upward translocation of acetochlor in wheat plants was due to its preferential distribution into root organelles with higher lipid contents. Conversely, the low bioconcentration of atrazine in root organelles and cell walls after uptake led to its easy upward translocation. Uptake of acetochlor and atrazine by wheat roots and the distribution of atrazine to the stems and leaves were predicted well by using the partition-limited model. The obtained results indicated that residual atrazine in soil may be taken up by wheat roots and acropetally translocated, thereby posing a threat to product safety of wheat.
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Atrazina/metabolismo , Herbicidas/metabolismo , Poluentes do Solo/metabolismo , Toluidinas/metabolismo , Triticum/fisiologia , Atrazina/toxicidade , Folhas de Planta , Raízes de Plantas , Poluentes do Solo/toxicidade , Toluidinas/toxicidadeRESUMO
The existing form of an ionizable organic compound can simultaneously affect its soil adsorption and plant bioactivity. In this experiment, the adsorption and bioactivity of two weak acid herbicides (WAHs), imazethapyr and 2,4-D, were studied to explore the predominant mechanism by which the soil pH and the addition of biochar can influence the phytotoxicity of WAHs in soil. Then, the WAH concentration extracted by hollow fiber-based liquid-phase microextraction (CHF-LPME), the in situ pore water concentration (CIPW) and the added concentration (CAC) were employed to estimate the phytotoxicity. The results showed that with increased pH from 5.5 to 8.5, the phytotoxicity of the WAHs to rice increased about 1-fold in the soil, but decreased in aqueous solutions, the IC50 values for imazethapyr and 2,4-D at pH 5.0 were 3- and 2-fold higher than that at pH 8.0. In addition, the soil adsorption decreased, indicating that the adsorption process was the dominant factor for the variation of the phytotoxicity of the WAHs in the tested soil instead of the decreasing bioactivity. The concentration that inhibits plant growth by 50% (IC50) calculated by the CAC in different pH and biochar soils ranged from 0.619 to 3.826â¯mg/kg for imazethapyr and 1.871-72.83â¯mg/kg for 2,4-D. The coefficient of variation (CV) of the IC50 values reached 65.61% for imazethapyr and 130.0% for 2,4-D. However, when IC50 was calculated by CIPW and CHF-LPME, the CVs of the IC50 values decreased to 23.51% and 36.23% for imazethapyr and 40.21% and 50.93% for 2,4-D, respectively. These results suggested that CIPW and CHF-LPME may be more appropriate than CAC for estimating the phytotoxicity of WAHs.