Study on the regulation of plasma-activated water characteristics and its effects on soilless germination of maize seeds

An atmospheric-pressure plasma jet (APPJ) device was optimized by enlarging the plasma discharge region to enhance the production efficiency of plasma-activated water (PAW), particularly under air discharge conditions. The physicochemical properties of PAW were found to be strongly dependent on the working gas and treatment duration. Under the same discharge conditions, PAW prepared by air discharge contained higher concentrations of NO₃⁻ and NO₂⁻, whereas PAW prepared by Ar discharge was richer in O₃ and H₂O₂. Meanwhile, increasing the discharge time led to a continuous decrease in pH, accompanied by sustained increases in both conductivity and oxidation–reduction potential. In addition, the effects of PAW were further investigated under soilless conditions. The results indicated that PAW enhanced the water absorption capacity of seeds, while different PAW compositions induced varying degrees of modification to the seed coat. When the physicochemical properties of PAW were adjusted to the optimal range for maize seed growth, both germination rate and seedling growth were significantly promoted. These findings demonstrated the strong potential of PAW for agricultural applications.