Glyphosate (GLY) is considered the most used herbicide in the world and has been associated with several environmental contamination risks. Despite being partially degraded by soil microorganisms, its residues can negatively affect the growth of valuable non-target plants. Thus, there is a need to find new strategies that minimize its impacts and enhance crop tolerance to GLY, allowing a more advantageous and safer, use of this herbicide. Salicylic acid (SA) is a hormone-like substance, able to enhance the efficiency of the antioxidant (AOX) system in plants and their tolerance to oxidative stress. This study aimed to unveil the effects of SA (100 μM) on the oxidative status of Hordeum vulgare L. in response to GLY (30 mg kg-1). After 14 days of growth, the presence of GLY led to a significant inhibition of growth, an accumulation of hydrogen peroxide (H2O2) and superoxide anion (O2-), an increase in lipid peroxidation (LP), proline and non-protein thiols, a decrease of the content of reduced ascorbate (AsA) and an upregulation of AOX enzymes. The exogenous application of SA mitigated the effects of GLY on growth, amount of H2O2 and degree of PL. It has also contributed to the reduction of AsA content, production of non-protein thiols and increased AOX enzymatic activity, particularly superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and gluthatione S-transferase (GST). These results show a positive role of SA against GLY induced oxidative stress, by modulating the AOX capacity of barley plants. However, the observed phytotoxicity of GLY was so pronounced, that the ameliorating effect of SA on AOX defenses was not enough to significantly overcome the herbicide-induced oxidative damage.
Keywords: Antioxidant system; Barley; Herbicide; Oxidative stress; Phytohormones; Reactive oxygen species.
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