Effects of imazethapyr spraying on plant growth and leaf surface microbial communities in Arabidopsis thaliana

Imazethapyr (IM) is an acetolactate synthase (ALS)-inhibiting herbicide that has been widely used in recent years.However,IM spraying can lead to the accumulation of herbicide residues in leaves.Here,we determined the effects of IM spraying on the plant growth and leaf surface microbial communities of Arabidopsis thaliana after 7 and 14 days of exposure.The results suggested that IM spraying inhibited plant growth.Fresh weight decreased to 48% and 26% of the control value after 7 and 14 days,respectively,of 0.035 kg/ha IM exposure.In addition,anthocyanin content increased 9.2-fold and 37.2-fold relative to the control content after 7 and 14 days of treatment,respectively.Furthermore,IM spraying destroyed the cell structures of the leaves,as evidenced by increases in the number of starch granules and the stomatal closure rate.Reductions in photosynthetic efficiency and antioxidant enzyme activity were observed after IM spraying,especially after 14 days of exposure.The diversity and evenness of the leaf microbiota were not affected by IM treatment,but the composition of community structure at the genus level was altered by IM spraying.Imazethapyr application increased the abundance of Pseudomonas,a genus that includes species pathogenic to plants and humans,indicating that IM potentially increased the abundance of pathogenic bacteria on leaves.Our findings increase our understanding of the relationships between herbicide application and the microbial community structures on plant leaves,and they provide a new perspective for studying the ecological safety of herbicide usage.

Efficient removal of Cr(Ⅵ)and Pb(Ⅱ)from aqueous solution by magnetic nitrogen-doped carbon

The magnetic nitrogen-doped carbon (MNC) was prepared from polypyrrole by a simple high temperature calcination process in this paper. The structure and properties of MNC were analyzed by scanning electron microscope, Fourier transform infrared spectroscopy, X-ray diffraction, Brunner-Emmet-Teller, vibrating sample magnetometer, and X-ray photoelectron spectroscopy. The capacity of MNC to adsorb Cr(Ⅵ) and Pb(Ⅱ) was evaluated. The effects of the initial pH, dosage, concentration and temperature on the adsorption capacity of MNC were measured. MNC had a large specific surface area and a special porous structure. Its nitrogen and carbon sources were rich, and the ratio of carbon to nitrogen was fixed. The maximum Cr(Ⅵ)-adsorption capacity and maximum Pb(Ⅱ) adsorption capacity of MNC could reach 456.63 and 507.13 mg·g^(−1) at 318 K, respectively. The pseudo-second-order model was used to describe the adsorption kinetics of MNC, and the Freundlich model was employed to discuss its isotherms. The adsorption process was affected by the electrostatic force, the reducing reaction, pores and chelation. The results of this study suggest that MNC is a material with superior performance, and is very easily regenerated, reused, and separated in the adsorption process.

Metabolomic modulations in a freshwater microbial community exposed to the fungicide azoxystrobin

An effective broad-spectrum fungicide,azoxystrobin(AZ),has been widely detected in aquatic ecosystems,potentially affecting the growth of aquatic microorganisms.In the present study,the eukaryotic alga Monoraphidium sp.and the cyanobacterium Pseudanabaena sp.were exposed to AZ for 7 days.Our results showed that 0.2–0.5 mg/L concentrations of AZ slightly inhibited the growth of Monoraphidium sp.but stimulated Pseudanabaena sp.growth.Meanwhile,AZ treatment effectively increased the secretion of total organic carbon(TOC)in the culture media of the two species,and this phenomenon was also found in a freshwater microcosm experiment(containing the natural microbial community).We attempted to assess the effect of AZ on the function of aquatic microbial communities through metabolomic analysis and further explore the potential risks of this compound.The metabonomic profiles of the microcosm indicated that the most varied metabolites after AZ treatment were related to the citrate cycle(TCA),fatty acid biosynthesis and purine metabolism.We thereby inferred that the microbial community increased extracellular secretions by adjusting metabolic pathways,which might be a stress response to reduce AZ toxicity.Our results provide an important theoretical basis for further study of fungicide stress responses in aquatic microcosm microbial communities,as well as a good start for further explorations of AZ detoxification mechanisms,which will be valuable for the evaluation of AZ environmental risk.

Enantioselective effects of imazethapyr residues on Arabidopsis thaliana metabolic profile and phyllosphere microbial communities

Imazethapyr(IM)is a widely used acetolactate synthase-inhibiting chiral herbicide.It has long-term residuals that may be absorbed by the human body through the edible parts of plants,such as vegetable leaves or fruits.Here,we selected a model plant,Arabidopsis thaliana,to determine the effects of R-IM and S-IM on its leaf structure,photosynthetic efficiency,and metabolites,as well as the structures of microorganisms in the phyllosphere,after 7 days of exposure.Our results indicated enantiomeric differences in plant growth between R-IM and S-IM;133μg/kg R-IM showed heavier inhibition of photosynthetic efficiency and greater changes to subcellular structure than S-IM.R-IM and S-IM also had different effects on metabolism and leaf microorganisms.S-IM mainly increased lipid compounds and decreased amino acids,while R-IM increased sugar accumulation.The relative abundance of Moraxellaceae human pathogenic bacteria was increased by R-IM treatment,indicating that R-IM treatment may increase leaf surface pathogenic bacteria.Our research provides a new perspective for evaluating the harmfulness of pesticide residues in soil,phyllosphere microbiome changes via the regulation of plant metabolism,and induced pathogenic bacterial accumulation risks.