# Experimental Investigation into the Influence of Plasma Technology on Seed Surface Wettability
## 3 Results  
The representative snapshot of the water droplet on the sunflower seed surface can be seen in Figure 1. The results of the measurements are presented in Figures 2-7. The effects of plasma treatment on the apparent water contact angle on the pea seed surface are demonstrated in Figure 2 (APD treatment) and Figure 3 (LPMD treatment), on the wheat seed surface in Figure 4 (APD treatment) and Figure 5 (LPMD treatment), and on the sunflower seed surface in Figure 6 (APD treatment), and Figure 7 (LPMD treatment), respectively. As shown in Figure 2, the untreated control variant of the pea seeds had a hydrophobic surface with an apparent contact angle of 113\({}^{\circ}\). It is also evident that the APD treatment had a relatively small influence on the apparent water contact angle. The angle decrease was observed only in the case of 10 s treatment for both gas flows, but it is statistically significant only for the flow of 30 SCFH (\(p\) = 0.001, 4% decrease). The other variants show either minor (nonsignificant) contact angle changes or even slight, statistically significant increases (\(p\) = 0.008, 5% increase for 30 s treatment duration; \(p\) = 0.000, 9% increase for 60 s treatment duration). Completely different results were obtained with LPMD treatment (see Figure 3). All treated variants showed significant changes in apparent water contact angle compared to the untreated variant (\(p\) < 0.020 for all). At a power of 500 W, the contact angle gradually decreased with increasing treatment duration, but the longest time (60 s) is the exception. The continuing decreasing trend was not found there. The lowest contact angle was 45% lower than for the control sample (\(p\) = 0.000) at a treatment time of 30 s. A similar trend was found at the power of 800 W. At the treatment duration of 30 s, approximately 50% lower contact angle was found compared to the control (\(p\) = 0.000). A slight nonsignificant increase was observed when the treatment time was extended from 30 s to 60 s (\(p\) = 0.970). Figure 1: Water droplet on the sunflower seed surface and its evaluation by Autodesk Inventor, 2018 software. The results of APD treatment on apparent water contact angle on the wheat seed surface are fully inconclusive (see Figure 4). The only decrease, of approximately 4%, compared to the untreated sample (hydrophobic surface with the contact angle of 108\({}^{\circ}\)), was observed for 30 s treatment duration at 30 SCFH airflow. However, it was still statistically nonsignificant (\(p\) = 0.063). On the contrary, all other variants had a higher contact angle of up to 11% for 10 s treatment duration at 30 SCFH flow. In contrast, only variant T30F50 resulted in a nonsignificant increase in contact angle compared to the untreated one. Hence, it seems that there is no causation between the APD process parameters and the apparent water contact angle. Figure 3: Effect of LPMD treatment on water contact angle on the surface of the pea seeds (the letter signs the variants that are not significantly different; vertical lines denote standard deviation bars). Figure 2: Effect of APD treatment on water contact angle on the surface of the pea seeds (the same letter signs the variants that are not significantly different; vertical lines denote standard deviation bars). The results of the LPMD treatment of wheat seed in Figure 5 are much more promising. Though 10 s treatment had a weak influence on the contact angle for both used power, a more extended treatment more substantially reduced the contact angle. At a power of 500 W, the treatment duration of 30 s caused a significant drop in the contact angle (approximately 78\({}^{\circ}\), \(p=0.000\)), but a more prolonged treatment had no significant additional effect. On the contrary, at a power of 800 W, the apparent water contact angle was continuously significantly decreased for further treatment.