Research on the Physio-Biochemical Mechanism of Non-Thermal Plasma-Regulated Seed Germination and Early Seedling Development in Arabidopsis

Abstract

Non-thermal plasma holds great potentials as an efficient, economical, and eco-friendly seed pretreatment method for improving the seed germination and seedling growth, but the mechanisms are still unclear. Therefore, a plant model organism Arabidopsis thaliana was used to investigate the physio-biochemical responses of seeds to non-thermal plasma at different treatment times by measuring the plant growth parameters, redox-related parameters, calcium (Ca2+) level and physicochemical modification of seed surface. The results showed that short-time plasma treatment (0.5, 1, and 3 min) promoted seed germination and seedling growth, whereas long-time plasma treatment (5 and 10 min) exhibited inhibitory effects. The level of superoxide anion (O2•−) and nitric oxide (NO) and the intensity of infrared absorption of the hydroxyl group were significantly higher in short-time plasma treated Arabidopsis seeds, and the level of hydrogen peroxide (H2O2) was remarkably increased in long-time plasma treated seeds, indicating that O2•−, ·OH, and NO induced by plasma may contribute to breaking seed dormancy and advancing seed germination in Arabidopsis, while plasma-induced H2O2 may inhibit the seed germination. The intensity of hydroxyl group and the contents of H2O2, malondialdehyde, and Ca2+ in Arabidopsis seedlings were obviously increased with the plasma treatment time. Catalase, superoxide dismutase, and peroxidase activities as well as proline level in short-time treated seedlings were apparently higher than in control. The etching effects of plasma on seed surface were dose-dependent, spanning from slight shrinkages to detached epidermis, which also significantly increased the oxidation degree of seed surface. Therefore, the improved activities of antioxidant systems, moderate ·OH, H2O2, and Ca2+ accumulation and seed surface modification induced by plasma all contribute to the enhanced seedling growth of Arabidopsis after short-time plasma treatment.

Mechanisms of Plasma-Seed Treatments as a Potential Seed Processing Technology

“…This brings attention to the fact that this process needs to be delicately handled. For example, Cui et al [55] used tape to prevent the movement of seeds during the plasma treatment but this may affect the seed coat especially if it is done in the presence of moisture. As a result, it seems that there is a limit to how much information can be extracted from surface analysis using microscopy.…”

“…Oxidation of the seed coat is very often observed but this can be propagated internally since there can be an increase in maldonaldehyde (MDA), a product of lipid peroxidation, after plasma treatment as seen by both Los et al [57] and Cui et al [55]. This may be among the first steps in the signal transduction considering that lipid peroxidation does not rely on enzymatic activity, which is very limited in dry seeds [140].…”

Plasma agriculture: Review from the perspective of the plant and its ecosystem

“…The results could also explain why prolonged treatment times correlate with negative effects on the germination of seeds, as observed by other authors. [73,[79][80][81]83,86,97]…”

Physicochemical surface analysis and germination at different irrigation conditions of DBD plasma‐treated wheat seeds

“…A small concentration of potassium atoms also appeared at the surface of the plasma-treated wheat seed and increased with the plasma treatment time to reach approximately 4% after 900 s. Surface diffusion of potassium or calcium has been reported for quinoa and Arabidopsis seeds exposed to plasma in studies that illustrated how the surface state of plasma-treated seeds becomes activated by the accumulation of ions and other charged groups. [6,45] High-resolution K2p spectra ( Figure S4) clearly revealed the increase in the amount of segregated potassium as a function of the treatment time. The diffusion of potassium from the interior to the outer layers of the wheat seed is presumably propelled by the polar character of the plasma-generated oxygencontaining functionalities groups on the seed surface and/or by variations in the surface potential during plasma treatment.…”