# Experimental Investigation into the Influence of Plasma Technology on Seed Surface Wettability
## 2 Materials and Methods
### Plasma Treatment  
Two utterly different plasma discharges were used in our experiments. Firstly, the Gliding Arc type plasma discharge burning at atmospheric pressure in open space (APD), and secondly, the microwave plasma discharge generated at low pressure in a vacuum chamber (LPMD).  
The APD system consists of a high voltage source with working gas control, an air compressor, and a plasma jet. The plasma jet was powered by a high-voltage power supply GVN1k 2011 supplied by Radan Ltd. (Barchov, Czech Republic) with a power input of 1.3 kW operating at a frequency of 50 Hz. The ignited discharge was blown out by working gas flow from the area between divergent stainless steel electrodes toward the treated sample. Compressed air was used as the carrier gas. The minimal overpressure of the compressed gas at the inlet into the plasma system was maintained at values of 600 kPa by the air compressor PKS 9-2/100 supplied by Orlik-Kompresory (Ceska Trebova, Czech Republic). The gas flow was controlled by the FL-2008 flow meter provided by Omega Engineering Inc. (Norwalk, CT, USA). It can change the gas flow in the range from 10 to 100 SCFH (gas flow 1 Nm\({}^{3}\).h\({}^{-1}\) corresponds to 35.3 SCFH). The electric field distribution in the vicinity of electrodes was described in detail in [22; 23].  
Only two different process parameters used in APD treatment, particularly carrier gas flow and treatment duration, were considered to vary. The working gas flow of 30 and 50 SCFH was used. The treated seeds were exposed to plasma discharge for 10, 30 and 60 s, respectively. The distance between the edge of the plasma jet and the seed surface was 8 cm for all the prepared samples. Hereafter, the APD treated variants are signed TxxFyy, where xx indicates the treatment time and yy denotes the working gas flow used.  
The LPMD consists of a stainless steel vacuum chamber, a microwave power generator, and vacuum pumps. The MNG 1K-08 power supply supplied by Radan Ltd. (Barchov, Czech Republic) generates pulsed microwave plasma with output power in the range of 100 to 850 W. The working pressure in the vacuum chamber was maintained at the value of 50 Pa using two rotary oil pumps connected in series, RV100/1 supplied by Lavat Plc. (Radim u Kolina, Czech Republic) and Adixen 2015 SD provided by Pfeiffer Vacuum Components & Solutions Ltd. (Aflar, Germany). Simultaneously, a small flow of dry air as working gas is added into the recipient via the FV 201-CV valve system and mass flow meters supplied by Bronkhorst High-TechH B.V. (Ruurlo, The Netherlands). The experimental set-up of LPMD is described in more detail in [24; 25].  
The parameters of the LPMD processes varied in microwave power and duration time. The treatment process used pulsed microwave power at values of 500 and 800 W. The treated seeds were exposed to plasma discharge for 10, 30 and 60 s. The working pressure in the vacuum chamber was maintained at 50 Pa for all treatment processes. Hereafter, the LPMD treated variants are signed TxxPyyy, where xx indicates the treatment time and yyy denotes the power used.