We designed a system to produce atmospheric hybrid cold-discharge plasma (HCP) based on microcorona discharge on a single dielectric barrier and applied it to inactivate microorganisms that commonly attach the rice seed husk. The cold-plasma treatment modified the surface of the rice seeds, resulting in accelerated germination and enhanced water imbibition. The treatment can operate under air-based ambient conditions without the need for a vacuum. The cold-plasma treatment completely inactivated pathogenic fungi and other microorganisms, enhancing the germination percentage and seedling quality. The final germination percentage of the treated rice seeds was ∼98%, whereas that of the nontreated seeds was ∼90%. Microcorona discharge on a single dielectric barrier provides a nonaggressive cold plasma that can be applied to organic materials without causing thermal and electrical damage. The hybrid nonthermal plasma is cost effective and consumes relatively little power, making it suitable for the surface sterilization and disinfection of organic and biological materials with large-scale compatibility.

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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.

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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.

Low temperature condition during December to January can limit seed emergence and seedling establishment for peanut production in Thailand. The objective of this study was to determine the effects of peanut seed priming on seed germination and vigor under optimal and low temperature conditions before and after 9 months of storage. Tainan 9 peanut seeds were primed with salicylic acid (SA), ascorbate (ASA), CaCl2, or chitosan and tested for germination at 25°C (optimal temperature) and 15°C (low temperature) before and after a 9-month storage period. Seed priming with 50 mg·L−1 SA and 50 mg·L−1 ASA for 12 hours before germinating improved germination at 15°C when compared to untreated seeds both before and after 9-month storage. The high seed quality, illustrated by high germination percentage, high seed vigor, and low mean germination time related to the low autoxidation substrates: lipoxygenase (LOX), malondialdehyde (MDA), and high antioxidants: superoxide dismutase (SOD) and catalase (CAT). It suggests that peanut seed priming with salicylic acid and/or ascorbate can improve seedling emergence and growth under low temperature conditions.

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