The Effect of Plasma Activated Water on the Rhizosphere Composition of Arabidopsis and Solanum lycopersicum

The emerging field of plasma agriculture investigates the potential benefit of non-thermal plasma (NTP) for agricultural practices. NTP-treated water, referred to as plasma activated water (PAW), has been proposed as a sustainable alternative to conventional nitrogen (N) fertilizers. Growing demand for N fertilizer is concomitant with increased global food demands. PAW contains nitrate (NO3-) and reactive oxygen species, such as hydrogen peroxide (H2O2), which are fixed from atmospheric molecules via NTP. While early studies report positive effects of PAW on plant growth, its influence on plant-associated microbial communities remains poorly understood. Here, we compared the impacts of PAW or NO3- solutions on the rhizosphere microbial community of Arabidopsis thaliana and Solanum lycopersicum. PAW was generated by a radio frequency (RF) glow discharge plasma source and contained no measurable ROS, while the control solution contained an equivalent concentration of NO3-. No significant differences in alpha diversity were detected in either plant species microbiome after 5 weeks of treatment when grown in non-commercial potting substrate. Significant dissimilarity was found in terms of beta diversity, but the relative abundance of the sequenced genera suggested no functional differences in rhizosphere communities. Overall, PAW treatment did not adversely impact the rhizosphere microbiome in either Arabidopsis or tomato. These results support the use of PAW as an alternative N-fertilizer, though outcomes may differ for PAW solutions containing ROS.