Salicylic Acid Pretreatment Modulates Wheat Responses to Glyphosate

Glyphosate is an extensively used herbicide because of its non-selective action for weed control. Salicylic acid (SA) is a phenolic compound that has the potential to increase plant tolerance to diverse stresses. To test SA ability to modulate plant responses to glyphosate we used young wheat (Triticum aestivum L.) seedlings grown as a water culture. Plants were sprayed with 1 mM SA, and 24 h later with 0.5 mM glyphosate. All measurements were performed 14 days after herbicide treatment. Wheat growth was reduced by glyphosate. Stress markers (proline and malondialdehyde) were significantly increased by glyphosate showing oxidative damages. Incapacity of wheat to cope with the oxidative stress was evidenced by reduction in thiols and phenolics content, accompanied by slight induction of superoxide dismutase and catalase activities. Enhanced activities of peroxidase, glutathione reductase and glutathione-S-transferase were expected to participate in glyphosate detoxification. SA applied alone had no important effects on measured parameters. SA pretreatment decreased stress markers and caused additional amplification of antioxidant defense systems in glyphosate-treated plants. Growth was partially restored in combine-treated plants due to SA application. SA probably triggered antioxidant defense to cope with the herbicide stress.