Responses of Rice Seed Quality to Large-Scale Atmospheric Nonthermal Plasmas

Abstract

Atmospheric nonthermal plasma (ANTP) is used for various biological applications including seed quality improvements in crop production. However, the underlying mechanisms of plasma-induced seed action are not fully explained and operating large-scale ANTP on seeds is highly challenging. Two large-scale ANTPs, streamer corona plasma (SCP) and dielectric barrier discharge (DBD) plasma, were used to enhance rice seed vigor through surface modification and functionalization. The SCP and DBD plasma were conducted under the same power source and applied to rice seeds to modify their surface from being highly hydrophobic to being highly hydrophilic, as defined by the apparent contact angle measurement. The results show that SCP requires less treatment time (~ 2 min) for surface activation than the DBD plasma process (~ 10 min). Both plasma-treated seeds showed higher seed vigor than non-treated seeds. For 50% of the viable seeds to emerge, the SCP-treated seeds took on average about 62 h., while the untreated rice seeds took around 72 h. The germination percentage of all conditions is ~ 92% which is a typical proportion of good seed quality. The microstructure of the rice seed surface suggests that the bombardment of highly energetic ions and the reaction of reactive oxygen and nitrogen species on the seed surface cause morphological changes via surface etching and functionalization without any adverse effects on seed nutrition. Graphical abstract: [Figure not available: see fulltext.]