Abstract:

In order to explore the regulation effect of melatonin (Mel) on degradation of residual pesticide in cucumber, cucumber variety ‘Y3F604’ was taken as test material and the carbamate pesticide propamocarb (C₉H₂₀N₂O₂) was applied to study the effect of 1 mmol/L Mel on propamocarb residues by irrigating the root. At the same time, the content of O₂^-·, H₂O₂, MDA, GSH and GSSG, and the change of antioxidant enzymes and detoxification enzymes after the application of propamocarb were investigated. The results showed that the exogenous application of 1 mmol/L Mel significantly reduced pesticide residues in cucumbers after the propamocarb treatment for 48 h. Under the stress of propamocarb, the content of O₂^-·, H₂O₂ and MDA in leaves increased significantly, while exogenous Mel treatment could effectively inhibit the accumulation of O₂^-·, H₂O₂ and MDA in cucumber. Compared with the control, exogenous Mel treatment could significantly increase the activity of cucumber SOD, CAT, POD, APX and GPX under the stress of propamocarb, and further increase the content of GSH and total glutathione, the ratio of GSH/GSSG, as well as the activity of GST and GR. Therefore, exogenous Mel treatment could induce the ability of antioxidant and detoxification under the stress of propamocarb, thus promoting the metabolism of propamocarb in cucumber. This study provides a new way to promote the degradation of pesticide residues in vegetables.

Key words: cucumber, melatonin, propamocarb, antioxidant enzyme, detoxification enzyme