The dissipation and risk assessment of 2,4-D sodium, a preharvest anti-fruit-drop plant hormone in bayberries

Pesticide multi-residues in Dendrobium officinale Kimura et Migo: Method validation, residue levels and dietary exposure risk assessment

Dendrobium officinale Kimura et Migo (D. officinale) is a dual-use plant with both botanical medicine and food applications, drawing increasing attentions. Pesticides are inevitably applied on D. officinale in commercial artificial-sheltered cultivation, yet little is known about pesticide residue levels in D. officinale. A modified high through-put QuEChERS method coupled with HPLC-MS/MS was developed and validated to detect 76 pesticides in D. officinale. Graphitized multi-wall carbon nanotubes (g-MWCNTs) was selected as the clean-up sorbent, showing relative weak affinity to triazole fungicide having planar structure in their molecular and low matrix effects of pesticides in D. officinale samples compared to MWCNTs and pesticarb. The validated method was applied to analyze pesticide residues in 86 real D. officinale samples collected from three main producing provinces. 43 different pesticides were detected with highest residue of 6.11 mg/kg for dimethomorph. Given possible health risks related to pesticide residues, accordingly, risk assessment of human exposure to pesticides via intake of D. officinale was thus performed, indicating that the pesticide residue in fresh or dry D. officinale would not cause potential risk to human health either in the long-term or short-term. This work improved our understanding of potential exposure risk of pesticide multi-residues in D. officinale.

Influence of 2,4-D residues on the soil microbial community and growth of tree species

The 2,4-D (2,4-dichlorophenoxyacetic acid) has low half-life in the soil, but it is capable of altering the soil microbial community. The objective of this study was to evaluate the influence of 2,4-D residues on the structure of the soil microbial community and the growth of tree species. The tolerance and phytoremediation potential of tree species were evaluated. The microbial analysis was performed by T-RFLP. The 2,4-D herbicide reduced the plant height of K. lathrophyton, number of leaves of C. ferrea and K. lathrophyton and root dry matter allocation for C. brasiliense, I. striata, P. heptaphyllum, and T. guianensis. Cucumis sativus intoxication on soil contaminated with 2,4-D was not significant. The structure of Fungi community in the rhizospheric soils of C. ferrea was altered. The herbicide 2,4-D increased the diversity of Fungi in rhizospheric soils of P. heptahyllum and R. grandis. Most tree species were tolerant, and the evaluation time was sufficient to remedy 2,4-D. The structures of the microbial communities Archaea, Bacteria, and Fungi were little influenced by 2,4-D. The diversity of the Archaea domain was not affected, the diversity of the Bacteria in Inga striata decreased while the fungi increased in Protium heptaphyllum and Richeria grandis with 2,4-D.

Effects of 2,4-Dichlorophenoxyacetic Acid on Cucumber Fruit Development and Metabolism

The auxin-like compound 2,4-dichlorophenoxyacetic acid (2,4-D) has been widely used as a plant growth regulator in cucumber fruit production; however, its influence on fruit development and metabolism has not been evaluated. In this study, the phenotype of cucumber fruits in both 2,4-D treatment and non-treatment control groups were recorded, and the metabolome of different segments of cucumber fruit at various sampling time points were profiled by a standardized non-targeted metabolomics method based on UPLC-qTOF-MS. The application of 2,4-D increased the early growth rate of the fruit length but had no significant effect on the final fruit length, and produced cucumber fruits with fresh flowers at the top. The 2,4-D treatment also affected the cucumber fruit metabolome, causing significant changes in the stylar end at 4 days after flowering (DAF). The significantly changed metabolites were mainly involved in methionine metabolism, the citric acid cycle and flavonoid metabolism pathways. At the harvest stage, 2,4⁻D treatment significantly decreased the levels of flavonoids and cinnamic acid derivatives while increased the levels of some of the amino acids. In summary, exogenous application of 2,4-D can greatly alter the phenotype and metabolism of cucumber fruit. These findings will assist in exploring the mechanisms of how 2,4-D treatment changes the fruit phenotype and evaluating the influence of 2,4-D treatment on the nutritional qualities of cucumber fruit.