This research investigates the enhancement of barley's resistance to salt stress by integrating nanoparticles and employing a nanostructured CoO sensor for the electrochemical detection of hydrogen peroxide (HO), a crucial indicator of oxidative stress. The novel sensor, featuring petal-shaped CoO nanostructures, exhibits remarkable precision and sensitivity to HO in buffer solution, showcasing notable efficacy in complex analytes like plant juice. The research establishes that the introduction of FeO nanoparticles significantly improves barley's ability to withstand salt stress, leading to a reduction in detected HO concentrations, alongside positive impacts on morphological parameters and photosynthesis rates. The developed sensor promises to provide real-time monitoring of barley stress responses, providing valuable information on increasing tolerance to crop stressors.