The evaluation of seed deterioration is very important to control the quality of the seeds stored. This study aimed to investigate the potential of fast ethanol assay for seed quality assessment of maize stored under different conditions. The first experiment was to determine the incubating temperature, incubating time, and amount of seed used in the assay. The results showed that the best protocol for the detection of headspace ethanol was incubation of 3 g of maize seed with 20% moisture content (wet basis) in a 20 mL gas chromatography vial at 70 °C for 1.5 h. The assay induced approximately 200-700 µg.L-1 of headspace ethanol, which was sufficient to identify seeds with different vigour levels. In the second experiment, the optimal conditions were used for quality assessment in aged maize seed stored for 12 months under different storage conditions. The increase in the ethanol production of stored maize seed under the controlled conditions (15 °C and 20% RH in the hermetic seal) was lower than under ambient conditions. The ethanol production levels of maize seed samples at the start of storage was significantly lesser than at six months storage (p < 0.05). The test limitations in deteriorated seed with different cultivars and ages will be discussed.

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. 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 hours 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 hours for treated and ~69 hours 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 moisture content of the seed was linearly reduced due to an ionic wind with a velocity of ~4.7 m/s, 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 hours of storage in a ~99% RH environment, there was no difference in moisture content subsequently. Thus, plasma treatment combines the advantages of efficient imbibition and vigor enhancement, and is beneficial for long-term seed preservation.

We demonstrate atmospheric corona plasma can modify rice (Oryza sativa L.) seed surface wettability and eliminate attached microorganisms at ambient temperatures, which can enhance germination and extend shelf life. High electric field strength up to 10 5 V/cm at the electrode tips is the critical factor for generating corona discharge plasma and, consequently, providing reactive oxygen and nitrogen species (RONS) via electron-induced impact ionization. We show that the reactive species and ions are primarily responsible for enhanced seed surface wettability via water imbibition (WI) and apparent contact angle (ACA) measurement. A scanning electron microscope was employed to confirm that the cold corona plasma treatment can decontaminate seedborne pathogenic fungi. Sterilized seeds with better surface wettability are more likely to germinate and yield higher quality seedlings. In addition, we demonstrate the potential use of the corona plasma process for seed storage extension and quality retention through accelerated aging germination and decreased moisture content. Germination of treated seed after passing accelerated aging process is approximately 90%, similar to that of unaged and untreated seeds.

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

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