## 4 Discussion  
The two plasma sources compared in this study displayed comparable results regarding inactivation of bacterial spores on four different types of crop seeds, maximum germination and changes in seed surface hydrophilicity. The only statistically significant plasma source effect was observed for wheat seeds and WCA, with the volume-DBD showing significant lower WCA values after treatment compared to the CD plasma source. Specifically, inactivation of _B. atrophaeus_ spores by direct CAPP treatment displayed different efficiency depending on the crop species tested. Inactivation in barley showed large variations and ranged from 0 to 3.3 log\({}_{10}\) CFU/mL, with a mean inactivation of \begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{1}{c}{**Plant Species**} & \multicolumn{1}{c}{**Treatment**} & \multicolumn{1}{c}{**Volume-DBD**} & \multicolumn{1}{c}{**CD**} \\  & & **WCA (\({}^{\circ}\))** & \\ \hline \multirow{2}{*}{Barely} & Control & 115.5 \(\pm\) 6.0 & 115.7 \(\pm\) 5.6 \\  & Control gas & 111.3 \(\pm\) 9.6 & 115.3 \(\pm\) 5.4 \\  & CAPP 2 min & **89.1 \(\pm\) 9.1** & **80.2 \(\pm\) 34.1** \\  & CAPP 5 min & **63.4 \(\pm\) 9.5** & **89.6 \(\pm\) 31.3** \\  & CAPP 10 min & **56.2 \(\pm\) 12.6** & **68.1 \(\pm\) 39.7** \\ \hline \multirow{2}{*}{Wheat} & Control & 110.1 \(\pm\) 8.4 & 105.7 \(\pm\) 5.6 \\  & Control gas & **116.7 \(\pm\) 5.4** & 108.1 \(\pm\) 8.3 \\  & CAPP 2 min & **66.4 \(\pm\) 11.4** & **89.3 \(\pm\) 12.6** \\  & CAPP 5 min & **66.4 \(\pm\) 11.3** & **91.6 \(\pm\) 14.4** \\  & CAPP 10 min & **68.8 \(\pm\) 18** & **54.0 \(\pm\) 16.9** \\ \hline \multirow{2}{*}{Rapeseed} & Control & 108.9 \(\pm\) 2.9 & 109.2 \(\pm\) 4.2 \\  & Control gas & 109.5 \(\pm\) 5.3 & 107.8 \(\pm\) 5.6 \\  & CAPP 2 min & **62.2 \(\pm\) 8.4** & **63.0 \(\pm\) 13.7** \\  & CAPP 5 min & **57.4 \(\pm\) 10.8** & **49.9 \(\pm\) 11.5** \\  & CAPP 10 min & **52.7 \(\pm\) 12.5** & **45.7 \(\pm\) 7.5** \\ \hline \multirow{2}{*}{Lupine} & Control & 125.6 \(\pm\) 7.77 & 122.6 \(\pm\) 6.5 \\  & Control gas & 126.2 \(\pm\) 7.21 & 121.5 \(\pm\) 6.4 \\  & CAPP 2 min & **57.4 \(\pm\) 7.2** & **77.3 \(\pm\) 38.7** \\ \cline{1-1}  & CAPP 5 min & **60.4 \(\pm\) 6.6** & **69.6 \(\pm\) 50.4** \\ \cline{1-1}  & CAPP 10 min & **56.3 \(\pm\) 5.3** & **75.6 \(\pm\) 45.3** \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Effect of volume-DBD and CD treatment on the water contact angle (WCA) of the seed surface for the four plant species studied. Values represent mean \(\pm\) SD of 12 individual measurements for each treatment. Bold numbers indicate a significant difference in mean value relative to the control and gas control at the level of \(p\)\(\leq\) 0.05 (One-Way-Analysis-of-Variance, n = 12). \(0.85\pm 1.12\log_{10}\text{CFU}/\text{mL}\) across all treatments, leading to non-significant differences compared to the gas control set-up using argon flow only (Cg 2 min). From five minutes onwards, mean efficiency in inactivation of all other species tested was significantly higher than the gas control. Using a CAPP source with short plasma exposure did not result in significant inactivation of spores, while longer treatment times led to elevated reduction in viability. Overall mean inactivation in wheat, lupine and rapeseed reached \(1.1\pm 0.7\log_{10}\text{CFU}/\text{mL}\), \(1.7\pm 0.5\log_{10}\text{CFU}/\text{mL}\) and \(1.9\pm 0.4\log_{10}\text{CFU}/\text{mL}\), respectively, for 10 min volume-DBD, which is equal to 90% to 99% inactivation. On the other hand, inactivation detected for two minutes of direct CAPP treatment did not show significant differences compared to the gas flow control of argon in all crop species except rapeseed. The overall low mean inactivation and large span of data recorded for barley might result from its seed coat structures, which differ from the other crop species tested. Wrinkles or crevices might allow better attachment of spores and/or shielding of spores and microorganisms (Supplementary Figure S1).