DOI: 10.14457/tu.the.2024.414
title: Impact of dielectric barrier discharge plasma and plasma-activated water on kangkong (Ipomoea aquatica Forssk.) seed qualities, physiological, and biochemical changes

description: Dielectric barrier discharge (DBD) plasma and plasma-activated water (PAW) have emerged as sustainable technologies to improve seed quality and biochemical properties in various plants species. This study aimed to investigate the effects of DBD plasma and PAW treatments at different durations on seed physiology, growth, bioactive compounds, and antioxidant and antiglycation activities in kangkong (Ipomoea aquatica Forssk.). Two kangkong cultivars, cv. Pugun 19 and cv. Banhann, were treated with atmospheric DBD plasma for 5, 10, 15, and 20 min, alongside untreated control. Scanning electron microscope (SEM) images showed plasma exposure caused seed surface cracks that increased with longer treatment. Plasmatreated seeds had lower water contact angles and absorbed water more rapidly. Hydrogen peroxide (H2O2) content increased under plasma treatment. Malondialdehyde (MDA) showed the highest content in seeds treated for 20 min. Catalase (CAT) activity was significantly higher after 10 to 20 min of plasma treatment only in cv. Banhann. Ascorbate peroxidase (APX) and superoxide dismutase (SOD) activities showed no significant changes among plasma treatment in both cultivars. The highest germination percentage occurred after 5 min of treatment in cv. Pugun 19. Field emergence increased after 10 to 20 min of plasma exposure in both cultivars, except for a decline at 20 min in cv. Pugun 19. Microgreens and leafy greens grown from all plasma-treated seeds displayed greater fresh and dry weights compared to control. The content of chlorophylls and carotenoids in microgreens and leafy greens increased under all plasma treatments, as did chlorogenic and coumaric acid in microgreens. However, changes in total ascorbic acid, phenolics, flavonoids, caffeic acid, ferulic acid, and antioxidant and antiglycation activities depended on the cultivar and treatment duration. The storability of DBD plasma-treated seeds was investigated using seeds of cv. Pugun 19. The seeds were exposed to atmospheric DBD plasma for 5 min. After treatment, they were packaged in sealed aluminum foil bags and stored at room temperature (30°C) for 0, 2, 4, and 6 months. The results showed no significant differences in emergence percentage at 0, 2, and 6 months after storage (MAS). However, the germination percentage and field emergence of DBD plasma-treated seeds significantly declined at 4 and 6 MAS, respectively. The fresh and dry weights of both microgreens and leafy greens grown from DBD plasma-treated seeds significantly declined at 6 MAS. In microgreens, chlorophyll and carotenoid contents remained stable throughout the 6-month storage period, whereas a significant decline was observed in leafy greens as early as 2 MAS. Although total ascorbic acid, phenolic and flavonoid contents, as well as antioxidant and antiglycation activities, decreased in both microgreens and leafy greens by 6 MAS, the ABTS and antiglycation activities in microgreens showed no significant changes over the entire storage period. PAW was generated using a gliding arc plasma device by treating distilled water treated for 5, 10, and 15 min to produce PAW5, PAW10, and PAW15, respectively. Increasing the plasma treatment duration led to a decrease in pH, while the concentrations of H₂O₂, nitrite (NO₂⁻), nitrate (NO₃⁻), and electrical conductivity progressively increased. The effects of PAW, generated at different treatment durations, on the germination and vigor of kangkong seeds were investigated using three cultivars: cv. Phai-ngern, cv. Senee 20, and cv. Senafore 20. For the PAW treatments, seeds were soaked in and irrigated with PAW5, PAW10, or PAW15, while distilled water served as the control. PAW10 and PAW15 treatments resulted in higher germination percentages and germination indices, as well as lower MGT, although these differences were not statistically significant. The effect of PAW10 treatment on growth, physiological, and biochemical parameters in kangkong microgreens was further investigated. PAW10 treatment led to increased fresh and dry weights, along with higher chlorophyll, carotenoid, and lipid contents. Nitric oxide (NO) and MDA levels showed no significant differences among treatments. In contrast, PAW10 treatment increased H₂O₂ content and enhanced the activities of CAT, SOD, and APX. It also upregulated the relative gene expression of CAT and SOD, whereas APX gene expression was dependent on the cultivar and PAW treatment. Total phenolic and flavonoid contents, along with antioxidant activities, were elevated under PAW10 treatment. The levels of total ascorbic acid, ferulic acid, and vanillic acid were also improved, though these changes were influenced by both the cultivar and the PAW treatment.