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BACKGROUND Picolinate/picolinic acid compounds are an important class of synthetic auxin herbicides. To explore the herbicidal activity of 6‐pyrazolyl picolinate compounds, a series of 3‐chloro‐6‐pyrazolyl‐picolinate derivatives was designed and synthesized. RESULTS Twenty‐five 3‐chloro‐6‐pyrazolyl‐picolinate derivatives synthesized were tested for herbicidal activity and the IC50 value of compound c5 to the growth of Arabidopsis thaliana root was 27 times lower than that of the commercial herbicide clopyralid. Compound c5 displayed better post‐emergence herbicidal activity and broader (Picloram, Clopyralid, Aminopyralid) herbicidal spectrum at a dosage of 400 g ha−1 in comparison with clopyralid; it also was safe to wheat and maize at this dosage. Arabidopsis thaliana phenotypes and expression of auxin‐response genes demonstrated that compound c5 might be a novel auxin‐type herbicide. Molecular docking analyses revealed that compound c5 had stronger binding ability to receptor AFB5 (auxin signaling F‐box protein 5) than clopyralid. CONCLUSION These 6‐pyrazolyl picolinate compounds could be used as potential lead structures for the discovery of a novel synthetic auxin herbicide. © 2021 Society of Chemical Industry

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Drought is a major abiotic stress that restricts plants growth, development, and yield. Coronatine (COR), a mimic of JA-Ile, functions in plant tolerance to multiple stresses. In our study, we examined the effects of COR in tobacco under polyethylene glycol (PEG) stress. COR treatment improved plant growth under stress as measured by fresh weight (FW) and dry weight (DW). The enzyme activity assay indicated that, under osmotic stress conditions, the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) were enhanced by COR treatment. Histochemical analyses via nitrotetrazolium blue chloride (NBT) and 3,3′-diaminobenzidine (DAB) staining showed that COR reduced reactive oxygen species (ROS) accumulation during osmotic stress. Metabolite profiles revealed that COR triggered significant metabolic changes in tobacco leaves under osmotic stress, and many essential metabolites, such as sugar and sugar derivatives, organic acids, and nitrogen-containing compounds, which might play active roles in osmotic-stressed tobacco plants, were markedly accumulated in the COR-treated tobacco. The work presented here provides a comprehensive understanding of the COR-mediated physiological, biochemical, and metabolic adjustments that minimize the adverse impact of osmotic stress on tobacco.