A medium-scale volume dielectric barrier discharge system for short-term treatment of cereal seeds indicates improved germination performance with long-term effects

Abstract

Atmospheric pressure plasma has the potential of being applied in pre-harvest processes as a sustainable technology for seed and plant treatment. In this study, a medium-scale volume dielectric barrier discharge reactor with a power density of 53.5 mW/cm3 was developed and applied for continuous treatment of larger amount of seeds. Within the argon plasma, reactive oxygen and nitrogen species were observed by optical emission spectroscopy. Short-term plasma treatment in the range of seconds of wheat and barley seeds revealed improved germination performance accompanied by altered seed surface properties. Depending on the exposure time, plasma displayed a positive impact on maximum germination and germination speed in both species. In line with this, the t50 values were significantly decreased for plasma treated seeds compared to untreated seeds for wheat and barley. Cumulative germination was enhanced from 20% up to 53% after 27 h of germination for wheat seeds treated from 10 s to 60 s with plasma. Barley seeds respond to the short plasma treatment times with increased germination of 10%–23% after 24 h observation time. Moreover, the seed surface of both plant species became more hydrophilic after plasma treatment supported by a decrease in the water contact angle and an increase in hydrophilic functional groups being detected by x-ray photoelectron spectroscopy. Water uptake by seeds was moderately increased after 2 h of imbibition for both plant species. The positive effects of plasma treatment on germination performance were still detectable after storage of seeds for one and two months.