# Influence of a Helium-Nitrogen RF Plasma Jet on Onion Seed Germination
## 3 Results and Discussion  
Knowledge of the physical and morphological properties of seeds helps to adapt the cultivation, harvesting, and processing technologies to benefit from the yielding potential of plants and to minimize losses associated with seed harvesting, storage, and processing. Ambient air temperature was 23 \({}^{\circ}\)C and relative humidity was 41%. The maximum recorded temperatures of the seeds exposed to plasma are presented in Table 1. For the distance from the torch to the seeds of 20 mm, the temperature slightly increased with the treatment time. For the longest treatment time of 15 s, it was below 36 \({}^{\circ}\)C. For the distance enlarged up to 50 mm, increasing of treatment time resulted in significant rise of temperature of the sample, even up to 57.2 \({}^{\circ}\)C for 480 s, measured at the surface of the seeds. Onion seed samples subjected to the stimulation with cold plasma produced with the use of a radio frequency generator exhibited a moisture level in the range from 8.83% to 9.45%, and these values were not statistically significantly different from those in the control sample--9.18% (Table 1). Statistically significant differences were noted only between the control sample (33.46 N) and seeds treated for 15 s at the short distance (37.09 N) and for 480 s at the 50-mm distance between the reactor nozzle and the sample (27.44 N). The data presented in Table 1 also indicate that the stimulation of onion seeds with the plasma was not the cause of the changes in the value of the compressive force. The morphological structure of the seeds before and after plasma treatment is presented in Figure 2.  
Changes in the surface structure are quite subtle and hardly noticeable. Drastic and harmful alterations, such as fragmentation of the external layer, were not observed, even with the longest treatment time. However, some slight differences in the seed coat cell surface could indicate the change in the cell turgor pressure. An important trait of seed material is its ability to germinate quickly and to produce healthy sprouts in a specified time. The dynamics of the plasma-treated onion seeds germination process is presented in Figure 3 and Table 2. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & \multicolumn{2}{c}{**Maximum Seed**} & \\
**Time of Stimulation [s]; Distance** & **Temperature after Cold** & **Moisture Content [\%]** & **Compressive Force [N]** \\
**between Nozzle’s Outlet and** & **Plasma Stimulation [\({}^{\circ}\)C]** & & \\ \cline{2-3}
**Tested Material [mm]** & **Control—25.8** & **Control—9.18 \(\pm\) 0.05 \({}^{\mathrm{abc}}\)** & **Control—33.46 \(\pm\) 1.07 \({}^{\mathrm{ac}}\)** \\ \hline
2; 20 & 27.5 & 9.09 \(\pm\) 0.03 \({}^{\mathrm{abc}}\) & 34.34 \(\pm\) 1.06 \({}^{\mathrm{ab}}\) \\
5; 20 & 29.3 & 9.11 \(\pm\) 0.16 \({}^{\mathrm{abc}}\) & 33.72 \(\pm\) 0.66 \({}^{\mathrm{abc}}\) \\
10; 20 & 33.7 & 8.92 \(\pm\) 0.28 \({}^{\mathrm{ac}}\) & 34.02 \(\pm\) 1.55 \({}^{\mathrm{abc}}\) \\
15; 20 & 35.2 & 8.83 \(\pm\) 0.06 \({}^{\mathrm{c}}\) & 37.09 \(\pm\) 1.64 \({}^{\mathrm{b}}\) \\
60; 50 & 47.2 & 9.15 \(\pm\) 0.09 \({}^{\mathrm{abc}}\) & 34.07 \(\pm\) 0.76 \({}^{\mathrm{ab}}\) \\
120; 50 & 52.6 & 9.23 \(\pm\) 0.04 \({}^{\mathrm{ab}}\) & 31.69 \(\pm\) 1.55 \({}^{\mathrm{ac}}\) \\
240; 50 & 54.0 & 9.22 \(\pm\) 0.08 \({}^{\mathrm{ab}}\) & 30.20 \(\pm\) 1.31 \({}^{\mathrm{cd}}\) \\
480; 50 & 57.2 & 9.45 \(\pm\) 0.13 \({}^{\mathrm{b}}\) & 27.44 \(\pm\) 1.12 \({}^{\mathrm{d}}\) \\ \hline \hline \end{tabular}  
* \(\pm\) standard deviation; \({}^{\mathrm{abcd}}\)-average values in the column marked with the same letter are not statistically significantly different (\(p<0.05\)).  
\end{table} 
Table 1: Selected physical parameters of onion seeds. The exposure of onion seeds to cold plasma was found to exert an effect on energy and germination.