## 3 Results and Discussion  
### Viability of the Plasma-Treated C. pruinosa Spores  
Figure 2a shows the effect of soft plasma jet treatment on the viability of _C. pruinosa_ spores at a concentration of 5 x 10\({}^{7}\) spores/mL. All plasma treatments resulted in a reduction in the viability of the _C. pruinosa_ spores. The spores exposed to the plasma for 1 min were less sensitive than those exposed for 3 min or more. A 3 min treatment with the soft plasma jet resulted in 12% spore viability, indicating that the soft plasma jet significantly inactivated 88% of fungal spore cells. Spores that survived could germinate and grow as mycelia. This decreasing spore viability with increasing plasma treatment time agrees with previous results regarding APPJ treatment of _C. bassiana_ and _C. pruinosa_ spores [12; 13]. Although the viability of _C. pruinosa_ spores treated by the soft plasma jet is similar to that treated by the APPJ, there are important differences between this research and the previous study [13]. First, the APPJ in the previous study [13] was applied to the fungal sample by positioning it between a needle-shaped powered electrode and a surface electrode attached to the bottom of a microwell plate. For the point-to-surface electrode configuration, both plasma radicals and an electric field were applied to the fungal sample. Meanwhile, the soft plasma jet was applied to fungal samples in the region without an electric shock from an electric field. In the soft plasma jet, plasma radicals are generated through discharge between the coaxial electrodes, and plasma radicals can then be applied to the fungal samples away from the plasma discharge region. The soft plasma jet-treated _C. pruinosa_ spores exhibited reduced spore viability. Consequently, the viability of _C. pruinosa_ sporescan be controlled by a soft plasma jet that produces plasma radicals in the absence of an electric shock. Second, the soft plasma jet used air as the plasma working gas, but the APPJ [13] instead used \(Ar\) gas. Therefore, the atmospheric-pressure air plasma jet (i.e., the soft plasma jet) can generate unique reactive oxygen and nitrogen species different from those generated using the atmospheric-pressure \(Ar\) plasma jet (i.e., the APPJ). As described in Section 3.3, the atmospheric-pressure air plasma jet (i.e., the soft plasma jet) can generate considerable amounts of \(H_{2}O_{2}\) and \(NO_{x}\), but only a very small amount of \(OH\) radicals as compared to the APPJ. The concentrations of reactive oxygen and nitrogen species in the plasma-activated water produced by the soft plasma jet will be discussed in Section 3.3. To further study the long-lasting effect of plasma-induced reactive species on the spore viability, we treated _C. pruinosa spores_ using the plasma-activated water. For this experiment, the plasma-activated water was prepared by treating sterile de-ionized water for 3 min with the soft plasma jet. The  
Figure 2: (**a**) Viability of the _C. pruinosa_ spores treated by the atmospheric-pressure air plasma jet (soft plasma jet). The 1 st, 2 nd, 3 rd, 4 th, and 5 th bars of Figure 2a represent the viability of the control, 1 min, 2 min, 3 min, and 6 min plasma-treated _C. pruinosa_ spores, respectively. (**b**) Viability of the _C. pruinosa_ spores treated by \(H_{2}O_{2}\) solutions, \(HNO_{3}\) solutions, acid water, and UV light. The 6 th and 7 th bars of Figure 2b represent the viability of _C. pruinosa_ spores treated by acid water of pH 3.5 and plasma-generated UV light, respectively. _C. prruinosa_ spores were soaked in the plasma-activated water for 10 min and 1 h, respectively. As shown in Figure 2a, the plasma-activated water significantly reduced the spore viability with an increase of soaking time. This result suggests that plasma-induced long-lived reactive species (\(H_{2}\)O\({}_{2}\) and \(NO_{x}\)) play an important role in fungal spore inactivation.