Effect of low-pressure plasma-induced NO, OH, and NH reactive species on radish seedling growth

Plasma agriculture has recently gained tremendous attention to increase seed germination, seedling growth, and yield. Several factors influence plasma’s negative and positive effects on seeds. One of the major factors is the role of plasma-generated reactive nitrogen species (RNS). To unlock the role of RNS on the seeds, we treated the radish seeds using low-pressure RF plasma with N₂ as a feed gas for different treatment times. We used the radish seeds with two different seed coat colours (brown and grey) and treated them under two conditions (dry and wet). In the present study, we want to analyse the possible role of seed coat colour, humidity, and plasma treatment time on seed germination and seedling growth. We observed that humidity and plasma treatment time affected the seedling growth for the wet seeds. There was no change in the seed germination rate or total germination percentage for both dry and wet seeds. We conducted electron paramagnetic resonance spectroscopy to analyse the increased concentration of organic radicals in radish seeds after plasma treatment. Additionally, we used optical emission spectroscopy (OES) to investigate the generation of reactive species in the plasma reactor with both dry and wet seeds. We also explored OES measurements without seeds, using N₂ and air as feed gases at different pressures (100, 150, and 200 Pa). The OES spectra revealed that elevated concentrations of NO, OH, and NH in the wet seeds were responsible for the enhanced radish growth.