Antioxidant system status of cucumber plants under pesticides treatment

A plants’ physiology maybe affected by various pesticides through the activation or inactivation of different biochemical pathways in target and non-target plants. In response to pesticides as xenobiotics, plants activate their antioxidant defense systems through both enzymatic and non-enzymatic pathways. In this study, two of the most common pesticides used to control cucumber whiteflies, imidacloprid and dichlorvos were sprayed on cucumber seedlings. Treatment with both pesticides significantly increased the activity of superoxide dismutase, catalase, ascorbate peroxidase, guaiacol peroxide, and phenylalanine ammonia-lyase. Moreover, total protein, proline, total soluble carbohydrates, and total phenolic content showed a significant elevation in response to the treatment with both pesticides compared to the control. The effects of the separate use of pesticides resulted in variation in the peak day of physiological changes in treated plants. Further experiments showed that pesticide treatment leads to a significant decrease in polyphenol oxidase activity, but no significant changes in contents of hydrogen peroxide, malondialdehyde, and electrolyte leakage index were found. Our results suggest that imidacloprid and dichlorvos had profound effects on the physiological status of cucumber plants at recommended rates. Our data also showed that the responses were similar between the two pesticides with differences in response times following treatment.