## 3 Results
### PAW Increases the Total Root Length and Root Hair Number in the Arabidopsis Root  
To understand how the PAW treatment affects the kinetics on root elongation in _Arabidopsis_ during development, we monitored the changes in root length using solid media to see a more severe and significant effect of PAW component affecting the growth. The changes in the compositions of the nitrogen ions in the PAW were predicted to affect plant growth and development. As the result shows, the root length became significantly longer with the PAW5, 7, and 12 treatments from day 7 to day 15 after planting compared to the DW treatment (Figure 2). In contrast to the root length for the PAW5, 7, and 12 treatments, the root length was significantly shorter for the PAW 19 and 40 treatments compared to the DW treatment. At 7 days after planting, the root lengths in the PAW5 treated plants were increased to about 33% compared to DW (Figure 2). Furthermore, at 15 days after planting, the root lengths for the DW-treated seeds were 22.14 \(\pm\) 2.62 mm, and for PAW5, they were 41.38 \(\pm\) 3.44 mm showing an 87% difference in length (Figure 3). In contrast, the root lengths under the PAW19 and 40 conditions were suppressed compared to the DW treatment (Figure 2). The root length at 7 days after planting was 9.82 \(\pm\) 1.07 mm, which was about 28% shorter compared to the DW treatment, while at 15 days after planting, it was 39% shorter, indicating that the PAW40 condition was the most suppressed condition. It is indicated that the appropriate plasma treatment time is essential for plant growth and development, and if excessive, it inhibits growth (Figures 2 and 3). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **pH** & **Nitrite NO\({}_{2}\)\({}^{-}\)** & **H\({}_{2}\)O\({}_{2}\)** & **Nitrate NO\({}_{3}\)\({}^{-}\)** & **Conductivity** \\  & & **(mg/L)** & **(mg/L)** & **(mg/L)** & **(\(\mu\)s/cm)** \\ \hline Deionized Water(DW) & 5.74 \(\pm\) 0.06 & 0.00 & 0.00 & 0.00 & 1.53 \(\pm\) 0.13 \\ PAW5 min(PAW5) & 3.62 \(\pm\) 0.02 & 1.09 \(\pm\) 0.11 & 0.09 \(\pm\) 0.01 & 25.29 \(\pm\) 2.88 & 118.10 \(\pm\) 2.26 \\ PAW7 min(PAW7) & 3.34 \(\pm\) 0.03 & 1.24 \(\pm\) 0.12 & 0.14 \(\pm\) 0.01 & 49.05 \(\pm\) 2.61 & 218.50 \(\pm\) 9.64 \\ PAW12 min(PAW12) & 2.94 \(\pm\) 0.08 & 1.85 \(\pm\) 0.07 & 0.27 \(\pm\) 0.02 & 102.67 \(\pm\) 6.30 & 460.33 \(\pm\) 15.25 \\ PAW19 min(PAW19) & 2.62 \(\pm\) 0.07 & 3.68 \(\pm\) 0.12 & 0.88 \(\pm\) 0.04 & 204.87 \(\pm\) 8.74 & 972.93 \(\pm\) 32.41 \\ PAW40 min(PAW40) & 2.37 \(\pm\) 0.04 & 5.17 \(\pm\) 0.16 & 1.31 \(\pm\) 0.04 & 389.08 \(\pm\) 12.24 & 1847.00 \(\pm\) 70.19 \\ \hline \hline \end{tabular}  
* The results of the Table 1 are the mean \(\pm\) standard deviation (SD).  
\end{table} 
Table 1: Physicochemical properties of the plasma-activated water (PAW). Figure 1: Optical emission spectrum of the surface dielectric barrier discharge (SDBD) with air from 200 to 600 nm. Because the difference in the root length was only clearly visible 7 days after planting, we further checked more detailed morphological characteristics in the earlier stage of plant growth. At 5 days after planting, Col-0 grown on the plant medium did not show any differences in the root length. However, under closer examination using a stereo microscope, the number of root hairs increased by 84.83 \(\pm\) 9.21 for the DW treatment and by 112.00 \(\pm\) 5.25, 107.83 \(\pm\) 5.74, 100.50 \(\pm\) 8.11 and 92.66 \(\pm\) 6.18 for the PAW5, PAW7, PAW12, and PAW19 treatments, respectively (Table 2). Furthermore, the length of the root hairs was 550.01 \(\pm\) 138.61 \(\upmu\)m for the DW treatment and 284.06 \(\pm\) 63.12, 188.12 \(\pm\) 46.67, and 161.50 \(\pm\) 38.05 \(\upmu\)m for the PAW5, PAW12, and PAW19 treatments, which are shorter than that of the DW treatment by about 48% and 71% for the PAW5 and PAW19 treatment, respectively, (Table 2, Supplementary Figure S1,).