Characterization of physical and biochemical changes in plasma treated spinach seed during germination

Abstract

Despite the accumulating data on the effect of plasma on seed germination, mechanisms of plasma action need more extensive research. In a previous study, we observed that high voltage nanosecond pulsed plasma enhanced the germination of spinach seeds and subsequent seedling growth. As a follow-up study, we investigated the physico-chemical, biochemical, and molecular changes in seed after plasma treatment, focusing on the early germination stage, to elucidate mechanism(s) for the stimulating effects of plasma on seed germination. The primary radicle protruded from seeds exposed to high voltage nanosecond pulsed plasma (one shot) slightly faster than the control seeds. The hydrophilicity of the seed surface significantly increased after treatment with high voltage nanosecond pulsed plasma (one shot). However, a very subtle increase in water uptake by plasma treated seeds was observed. Raman and FTIR spectroscopy analyses on chloroform extract of seed coats demonstrated no significant chemical etching on the surface of plasma treated seeds. This may be related to no dramatic increase in water absorption by seeds. The level of GA hormone and starch hydrolysis inside the plasma treated seeds was significantly elevated within 24 h. Taken together, our results suggest that high voltage nanosecond pulsed plasma may not only enhance hydrophilicity of the seed surface but also stimulate biochemical and molecular processes inside seed, leading to enhanced embryonic development.

Aspergillus oryzae spore germination is enhanced by non-thermal atmospheric pressure plasma

“…Fungal spores in PBS and PDB were exposed to micro DBD plasma for 2 and 5 min, respectively, washed once with water, resuspended in 50 µL deionized water, and placed on a mounting plate and kept aside until the water evaporated. The dried spores were analyzed via FTIR as described previously 54 . Two replicate FTIR spectra measurements for each sample were averaged using Excel.…”

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

“…They showed that vacuum affected the auxin/cytokine balance, cold plasma increased GA, and EMF decreased the amount of ABA and increased IAA and SA without changing GA despite not being able to make a clear connection between phytohormones and germination kinetics. Ji et al [168,169] also observed an increase in GA in spinach seeds but did not measure any other hormones. The increase in GA may be the result of plasmaderived ozone [157] although it is often speculated that it is specifically auxin and cytokinins that are affected, which are hormones that increase and stimulate cell division, proliferation and elongation.…”

RNA Sequencing of Arabidopsis thaliana Seedlings after Non-Thermal Plasma-Seed Treatment Reveals Upregulation in Plant Stress and Defense Pathways

“…As stated previously, it is difficult to compare results across plasma-seed treatment studies due to the high number of variables, and if molecular analysis is performed, often specific genes are selected based on economic or health-related importance. In previous plasma agriculture studies, the genes that were targeted are related to germination, primary or secondary metabolisms, such as starch-degrading enzyme [ 11 ], drought-related resistance genes [ 12 ], antioxidant genes [ 13 ], pathogen resistance (PR) genes, and epigenetic regulation related genes [ 14 , 15 ], and plant-specific secondary metabolites with pharmacological uses [ 17 , 19 ].…”

“…Currently, the most common method for analyzing gene transcription in the plasma agriculture literature is qPCR, where specific genes of interest are targeted, but very few studies analyze genes in an unbiased manner using micro-arrays or RNA sequencing (RNA-seq) [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ]. Furthermore, these findings are often only relevant to that plant and may not be applicable elsewhere to understand the molecular mechanisms of plasma-seed treatments.…”