Advantages and Limitations of Surface Analysis Techniques on Plasma-Treated Arabidopsis thaliana Seeds

Abstract

Surface characterization of plasma-treated seeds has made significant progress over the last decade. Most papers in the literature use scanning electron microscopy (SEM) and contact angle goniometry to investigate surface modifications. However, very few papers address the chemical modifications to the seed coat after plasma treatment. Here, a summary of the methods used to analyze plasma-treated seeds is presented, such as SEM, contact angle goniometry, energy-dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). The results obtained on Arabidopsis thaliana Col-0 seeds and the limitations of these techniques are discussed. An experiment was designed in order to compare the relative advantages and limitations of these surface analysis techniques by investigating the separate effects of plasma, heat, and ozone on A. thaliana seeds.

An In Situ FTIR Study of DBD Plasma Parameters for Accelerated Germination of Arabidopsis thaliana Seeds

“…Since we observed that particular plasma conditions yielded a statistically significant effect on germination, plasma chemistry was compared between these conditions to identify the reason for this effect. Although a previous study used five surface analysis techniques on plasma-treated seeds, including SEM images [ 3 ], the focus of this study was to analyze plasma chemistry. Typical absorption spectra in the mid-infrared range of 2500–500 cm −1 , with 4 cm −1 resolution and 20 s acquisition periods are shown in Figure 2 .…”

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

“…Through seed surface modifications, it is also possible to alter ion homeostasis, which was indicated by downregulation in ion transport activity in Figure 8 A. Previous studies have shown ion redistribution after plasma treatment in cations such as calcium, magnesium, or potassium, migrating into the interior of the seed or being enriched on the surface [ 43 , 44 ]. This, however, could also be interpreted by the seed as damage and, therefore, could be a symptom of a plant stress response.…”

Entering the plasma agriculture field: An attempt to standardize protocols for plasma treatment of seeds

“…The mechanisms of plasma–seed treatments as a potential seed processing technology are reviewed by Waskow et al, [ 14 ] and some of the corresponding plasma devices found in the literature are listed in Figure 3. Among the papers cited in the present study, the most common plasma sources include planar dielectric barrier discharges (DBDs) in various forms as shown in Figure 3(1), [ 11–64 ] followed by DBD plasma jets as shown in Figure 3(2) [ 10,36,65–74 ] ; low‐pressure plasma in a vacuum chamber as shown in Figure 3(3) [ 28,43,75–89 ] ; and less common devices such as gliding arcs, [ 9,43,76,90 ] and corona arrays as shown in Figure 3(4). [ 43,91,92 ]…”

“…The various types of plasma sources in Figure 3 can be summarized as follows: A DBD generates plasma by time‐varying high voltage (kV) between two electrodes; the dielectric barrier is to prevent arcing between electrodes that could otherwise occur following the electrical breakdown of the gas. The planar DBD may generate the plasma in the volume of gas between opposing electrodes (VDBD), [ 12,17–41 ] or on the surface of a dielectric adjacent to the electrode edges (SDBD), [ 11,42–53 ] or with embedded electrodes (diffuse coplanar surface barrier discharge [DCSBD]). [ 54–59 ] In a plasma jet, there is usually a gas flowing in a thin tube with a DBD excitation that can be pulsed DC, or continuous AC, or radiofrequency (RF).…”

“…However, the possibility of metallic nanoparticle contamination of the seed coat should be borne in mind. [ 52 ] Electrodes can also be protected from the plasma by a type of lacquer or by embedding them in a dielectric as in the DCSBD of Roplass. [ 54 ] Higher voltages are required for embedded electrodes because the plasma is further from the electric field concentrated near the electrode edges, although the plasma is more uniform for the same reason.…”