Abstract
The multiple contamination of pesticides are common in farmland soil. However, there is a noteworthy knowledge gap regarding the ecophysiological response of co-exposure of pesticides on non-target crops under such conditions. Silicon (Si) was chosen to alleviate pesticides phytotoxicity due to its ability to improve plant growth and adaptive responses against xenobiotics exposure. This study explores the mechanisms of combined effects of lambda-cyhalothrin (CM), a synthetic pyrethroid insecticide and difenoconazole (DIF), a systemic triazole fungicide induced phytotoxicity and the potential of Si to alleviate CM + DIF toxicity by regulating growth, redox homeostasis, and antioxidant defense in tomato (Solanum lycopersicum L.) seedlings. The results showed that tomato growth and chlorophyll biosynthesis was significantly inhibited by individual and combined stress of CM and DIF, possibly due to induced oxidative stress. Interestingly, the extent of lipid peroxidation was much higher under CM and DIF co-exposure than under CM and DIF only, as indicated by MDA level, thus indicating the synergistic effect of pesticide on oxidative damage. Moreover, pesticide exposure significantly improved ascorbate peroxidase, peroxidase, glutathione S-transferase, reduced glutathione, and proline in tomato seedlings compared to control. Our study demonstrates that Si improves tomato seedling's tolerance to CM + DIF toxicity by enhancing pesticides metabolism through GSH-GST detoxification enzymes. Si supply also enhanced PAL activity and stimulated reactions in the phenylpropanoid pathway to produce phenolic and flavonoids in tomato seedlings under CM + DIF stress. Si promotes chlorophyll biosynthesis and reinforces the antioxidative system, thereby maintaining redox homeostasis and overall seedling growth under CM and DIF co-exposure. The findings provide valuable information about the underlying mechanisms of Si-mediated CM and DIF co-exposure response with potential use as effective bio-stimulants in agriculture to address pesticides phytotoxicity issues.