Effects of Cold Plasma Treatment on Physical Modification and Endogenous Hormone Regulation in Enhancing Seed Germination and Radicle Growth of Mung Bean

Abstract

This study investigated the effects of plasma duration and different reactive species ratios of cold atmospheric-pressure plasma treatment on both physical and endogenous hormone changes in enhancing the germination and growth of mung bean seeds. Seed germination and sprout stem length were significantly enhanced after plasma treatment. The germination rate increased eleven times after 12 h, while the radicles’ length increased ~3 times after 96 h with optimal plasma treatment parameters. SEM images showed that the plasmas directly induced gradual changes in the seed coating, including deformed and shrunken epidermis, and cracks with sizes varying from 0.2 to 1.5 µm after 4 min of plasma treatment. Water contact angle was reduced from 73° with untreated seed to almost 0° with 4 min treated seed. These effects could lead to better water absorption on the surface of treated seeds. We found that a plasma energy dosage of 0.08 Wh per seed and NO concentration between 20–95 ppm were the optimal enhancement conditions. We also showed that, for the first time, through delicate extraction, separation, and quantification processes, NO-induced upregulation of the natural growth hormone gibberellic acid could be the dominant phytochemistry pathway responsible for the enhancement effect.

Scanning electron microscopy, biochemical and enzymatic studies to evaluate hydro-priming and cold plasma treatment effects on the germination of Salvia leriifolia Benth. seeds

“…The surface of the treated seeds seemed The optical emission spectrum of low-pressure glow discharge in the air at the power of 80 (left) and 100 (Right) W. smoother, and even minute holes were observed (Figures 2-5). Our findings also agree with other reports in which CP is shown to increase the GP and GR of treated seeds (Nishime et al, 2020;Le et al, 2022).…”

“…In these experiments, like other studies, the incidence of more severe changes in the seed surface morphology increased as the CP treatment time increased (Figures 2-5) (Li et al, 2017). Therefore, the degree of seed coat deformation and the size of the cracks observed are proportional to the plasma exposure time (Le et al, 2022). As the surface of normal and uncovered seeds was different altogether, the changes in the seed surface morphology were also different.…”

“…Some technologies, such as scarification, leaching seed, removal of seed coverings or un-coating, red light, darkness, cold storage (short, moderate, and long period), cold stratifications, hydropriming, nanotechnology, and recently, cold plasma (CP), were used on the seeds of different plant species to overcome physical and physiological dormancy, and increase germination (Geneve, 2003;Ji et al, 2016;Hatami et al, 2017;Pang et al, 2021). CP treatment leads to improved seed germination and increased initial growth of plants, and boosts food-packaging characteristics (Sera et al, 2012;Saberi et al, 2018;Priatama et al, 2022;Le et al, 2022). CP contains lowtemperature particles, such as neutral molecules, atomic species, and relatively high-temperature electrons.…”

“…These events on the surface of seeds increases water uptake and stimulates the digestion of stored compounds that result in a significant increase in seed germination (Hoppanováet al, 2020;Filatova et al, 2020;Sajib et al, 2020). The scanning electron microscopy (SEM) images of mung bean seeds showed CP-induced cracks on the seed surface and that the water contact angle was decreased from 73°in untreated seeds to 0°in CP-treated seeds (Le et al, 2022). In addition to physical changes, the endogenous hormone balance changed, based on the time of CP exposure, as well as the ratio of different reactive species to CP.…”

“…In addition to physical changes, the endogenous hormone balance changed, based on the time of CP exposure, as well as the ratio of different reactive species to CP. The high percentage of nitric oxide (NO) in CP particles significantly enhances the activity of gibberellic acid (GA 3 ) hormone in seeds (Le et al, 2022). The activity of some enzymes, such as superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), is increased in plants treated with CP, and the level of lipid peroxidation (MDA) is decreased.…”