In situ mass spectrometry imaging reveals pesticide residues and key metabolic pathways throughout the entire cowpea growth process.

Cowpea plants, renowned for their high edibility, pose a significant risk of pesticide residue contamination. Elucidating the behavior of pesticide residues and their key metabolic pathways is critical for ensuring cowpea safety and human health. This study investigated the migration of pesticide residues and their key metabolic pathways in pods throughout the growth process of cowpea plants via in situ mass spectrometry. To this end, four pesticides--including systemic (thiram), and nonsystemic (fluopyram, pyriproxyfen, and cyromazine) pesticides--were selected. The results indicate the direct upward and downward transmission of pesticides in cowpea stems and pods. Systemic pesticides gradually migrate to the core of cowpea plants, whereas nonsystemic pesticides remain on the surface of cowpea peels. The migration rate is influenced by the cowpea maturity, logarithmic octanol-water partition coefficient (log Kow) value, and molecular weight of the pesticide. Further, 20 types of key metabolites related to glycolysis, tricarboxylic acid cycle, and flavonoid synthesis were found in cowpea pods after pesticide treatment. These findings afford insights into improving cowpea quality and ensuring the safe use of pesticides.

Hyphenated liquid electrode glow discharge-dielectric barrier discharge molecular emission spectrometry for determination of dithiocarbamates.

A hyphenated liquid electrode glow discharge (LEGD)-dielectric barrier discharge (DBD) molecular emission spectrometer was constructed and used as a novel liquid chromatography (LC) detector for dithiocarbamates (DTC) determination. The LEGD was used as an acidolysis reactor for the in-situ transformation of DTCs into CS2 with high efficiencies of 74.11-97.98%. The DBD was used to excite CS2 gas to generate a specific molecular emission at 257.94 nm. The linear correlation coefficient of the method was > 0.99 from 1 to 200 µg mL-1. The detection limits ranged from 0.1 to 0.3 µg mL-1 with 76-119% recovery and relative standard deviations of 0.2-8.5%. Moreover, the hyphenated microplasma spectrometer achieved low power consumption, low temperature, immediate acidolysis, and high transformational efficiency, and can detect each DTC when combined with LC.

Remarkably efficient Pt/CeO2-Al2O3 catalyst for catalytic hydrodeiodination of monoiodoacetic acid: Synergistic effect of Al2O3 and CeO2.

Monoiodoacetic acid (MIAA) is one of the highly toxic halogenated disinfection by-products, which is formed during water disinfection processes. Catalytic hydrogenation with supported noble metal catalyst is a green and effective technique for the transformation of halogenated pollutant, but its activity still needs to be identified. In this study, Pt nanoparticles were supported on CeO2 modified γ-Al2O3 (Pt/CeO2-Al2O3) by chemical deposition method and the synergistic effect of Al2O3 and CeO2 on catalytic hydrodeiodination (HDI) of MIAA was systematically studied. Characterizations revealed that Pt dispersion could be improved by the introduced CeO2 through the formation of Ce-O-Pt bond and MIAA adsorption could be facilitated by high Zeta potential of Al2O3 component. Furthermore, optimal Ptn+/Pt0 could be obtained by adjusting CeO2 deposition amount on Al2O3, which could effectively facilitate the activation of C-I bond. Therefore, Pt/CeO2-Al2O3 exhibited remarkable catalytic activities and TOF values compared with those of Pt/CeO2 and Pt/Al2O3. Through detailed kinetic experiments and characterization, the extraordinary catalytic performance of Pt/CeO2-Al2O3 can be attributed to the abundant Pt sites as well as the synergistic effect between CeO2 and Al2O3.

Synergistic effect of co-culture rhizosphere Streptomyces: A promising strategy to enhance antimicrobial activity and plant growth-promoting function.

Rhizosphere Streptomyces is one of the important types of rhizosphere microorganisms that plays an important role in promoting plant growth and controlling plant diseases to maintain agricultural ecosystem balance and green ecological agriculture development as beneficial bacteria. Microbial co-culture simulates the complex biocommunity in nature, which has more advantages than the monoculture with a synergistic effect. As the key signal mediums of microorganisms, plants, and their interactions, microbial metabolites are of great significance in revealing their functional mechanism. In this study, two potential plant growth-promoting rhizobacteria, Streptomyces albireticuli MDJK11, and Streptomyces alboflavus MDJK44, were selected to explore the effects of co-culture and monoculture on plant growth promotion and disease prevention, and the metabolic material basis was analyzed by metabonomics. Results showed that Streptomyces MDJK11, MDJK44 monoculture, and co-culture condition all showed good growth promoting and antimicrobial effects. Moreover, as compared to the monoculture, the co-culture showed the advantage of a synergistic enhancement effect. LC-MS-based metabonomics analysis showed the metabolic material bases of Streptomyces for plant growth promotion and disease prevention were mainly plant hormone and antibiotics and the co-culture condition could significantly stimulate the production of plant hormone promoters and macrolide, cyclic peptide, and aminoglycoside antibiotics. The study proved that the co-cultures of S. albireticuli MDJK11 and S. alboflavus MDJK44 have great potential in crop growth promotion and disease prevention.