# Characterization and Optimization of a Conical Corona Reactor for Seed Treatment of Rapeseed
## 4 Conclusions  
A corona discharge reactor with a horn-like nozzle was adapted for the treatment of small seeds. The discharge generated by this new configuration was characterized and its effects on rapeseed were investigated.  
Rapeseed seeds exposed to the plasma produced by the funnel-shaped reactor exhibited accelerated germination. Observed improvements concerning seed germination showed to be dependent on the discharge power. The ROS-rich plasma environment  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Treatment** & **G\({}_{\text{max}}\) (\%)** & **t\({}_{\text{50}}\) (h)** & **U\({}_{\text{25-75}}\) (h)** \\ \hline Ct & 92 \(\pm\) 2 & 21.3 \(\pm\) 0.6 & 5.8 \(\pm\) 0.2 \\ Ct\({}_{\text{g}}\) & 91 \(\pm\) 1 & 20.9 \(\pm\) 0.7 & 4.7 \(\pm\) 0.4 \\ D = 10\% & 92 produced by this reactor led to the incorporation of oxygen radicals at the seed coat contributing to the pronounced increase in surface wettability. Given the direct treatment approach, the number of seeds that can be put in between the electrodes was revealed to be an important parameter regarding process homogeneity and reproducibility.  
The conical configuration of the reactor presented in this study is designed for the treatment of small numbers of seeds and basic science investigations. However, considering the positive results on seed germination and surface wettability improvement, a large-scale corona reactor (possibly working with air) can be easily manufactured for certain future field applications.  
Given the large variety of plasma sources already studied for applications in agriculture, each plasma system intended for seed treatment has to be individually investigated and optimized. The set of parameters determined to obtain specific results is unique for each plasma source. In addition, in direct systems, such as the funnel reactor, the biological target strongly affects the plasma treatment (homogeneity and expected results). Therefore, the precise adjustment of discharge parameters is of utmost importance to reach positive results, and also the process has to be carefully investigated for seeds from other plant species.  
Conceptualization, T.M.C.N., T.S.M.M. and H.B.; methodology, T.M.C.N., T.S.M.M. and J.W.; validation, T.M.C.N. and J.W.; formal analysis, T.M.C.N.; investigation, T.M.C.N. and J.W.; data curation, T.M.C.N. and N.W.; writing--original draft preparation, T.M.C.N.; writing--review and editing, T.M.C.N., N.W., K.G.K. and H.B.; supervision, H.B. and K.G.K.; project administration, K.G.K., H.B. and K.-D.W.; funding acquisition, K.G.K., N.W., H.B. and K.-D.W. All authors have read and agreed to the published version of the manuscript.  
This research was partly funded by the Federal Ministry of Education and Research of Germany (BMBF) within the framework of the project \"Physics for Food\" (No. 03 WIR 2805 A and 03 WIR 2808 D). Some authors ([PERSON] and [PERSON]) acknowledge financial support from the Coordination for the Improvement of Higher Personnel Education--CAPES, Brazil, under the program PrInt.  
Not applicable.  
The authors are grateful to [PERSON] and [PERSON] for technical assistance in the construction of the plasma reactor.  
The authors declare no conflict of interest.