Nitric oxide application alleviates fungicide and ampicillin co-exposure induced phytotoxicity by regulating antioxidant defense, detoxification system, and secondary metabolism in wheat seedlings.

Pesticides and antibiotics usually sink into soil, posing serious phytotoxic effects on plants. However, studies are elusive regarding the phytotoxic effects of fungicide Consento (CON) and antibiotic ampicillin (AMP) co-exposure. Nitric oxide (NO) is an important plant signaling molecule known for abiotic stress tolerance in plants. This study investigated the phytotoxic effects of CON and/or AMP on the growth and antioxidant activities of wheat (Triticum aestivum L.) seedlings and unveiled the underlying mechanisms induced by the application of NO as sodium nitroprusside (SNP; 100 μM) in wheat seedlings exposed to CON and/or AMP in a hydroponic culture. Results revealed that application of CON, AMP, and CON + AMP significantly reduced the shoot length (21, 27, & 42%), root length (49, 41, & 51%), shoot biomass (30, 27, & 35%), root biomass (51, 36, & 56%), Chl-a (24, 19, & 29%), Chl-b (42, 48, & 54%), and carotenoid contents (35, 33, & 35%), respectively, due to significantly higher hydrogen peroxide (231, 151, & 157%) and malondialdehyde production (97, 60, & 148%) in wheat seedlings compared to control plants. However, the application of NO significantly enhanced wheat lengths (38%), biomass (60%), and photosynthetic pigments (67%) on co-exposure to CON + AMP. Moreover, NO treatment significantly lowered hydrogen peroxide (36%) and malondialdehyde contents (35%) in wheat seedlings exposed to CON + AMP stress, indicating the protective role of NO in scavenging reactive oxygen species. Wheat seedlings exposed to the combined stress of CON and AMP regulated antioxidant defense, xenobiotic detoxification, and the phenylpropanoid pathway to combat stress conditions. However, NO application significantly increased CAT (44%), proline (60%), total phenolic (41%), nitrate reductase (53%), and polyphenol oxidase activities (31%) to mitigate CON + AMP stress. These findings suggest NO application as an effective and environmentally friendly approach for detoxification of CON + AMP stress through biosynthesis of secondary metabolic enzymes and regulation of antioxidants for boosting wheat crop resilience under pesticide and antibiotic co-contamination.