Effect of dielectric barrier discharge plasma on rice (Oryza sativa L.) seed hydration and hygroscopicity

Abstract

Abstract Nonthermal plasma has been explored as a green technology for improving seed wettability and crop productivity. In this investigation, we demonstrate scalable dielectric barrier discharge (DBD) plasma treatment of rice seeds at atmospheric pressure to elucidate the effect of plasma on seed hydration, hygroscopicity, and moisture content (MC). These properties are associated with seedling quality, nutrition, and shelf-life storage. The floating approach was utilized to evaluate seed wettability for a large-scale seed lot because treated seeds become superhydrophilic and sink immediately into water, whereas nontreated seeds float on the surface. We proved that a hydrophilic surface is necessary to improve water absorption, but the extent of physical etching and chemical functionalization had the greatest impact. After 5 h of imbibition, the seeds that were treated with plasma for 10 min absorbed ∼20% more water than the nontreated seeds. After plasma treatment, seed vigor increased dramatically, as evidenced by the radicle emergence times of ∼64 h for treated and ∼69 h for nontreated seeds. Furthermore, the treated seeds yielded seedlings that were ∼10% longer compared to the nontreated seeds on day 14 of germination, even after an artificial aging process. During treatment, the MC of the seed was linearly reduced due to an ionic wind with a velocity of ∼4.7 m s−1, which was generated using a localized nonuniform electric field that was applied around the seed’s surface. DBD plasma can modify seed coatings at the nanoscale level but not the availability of its primary nutrition and hygroscopicity. Although the treated seed absorbed moisture four times faster than the nontreated seed during the first 24 h of storage in a ∼99% relative humidity environment, there was no difference in MC subsequently. Thus, plasma treatment combines the advantages of efficient imbibition and vigor enhancement, and is beneficial for long-term seed preservation.