Direct treatment of pepper (Capsicum annuum L.) and melon (Cucumis melo) seeds by amplitude-modulated dielectric barrier discharge in air

This study evaluates low-temperature plasma generated by an amplitude-modulated dielectric barrier discharge (DBD) as a direct surface treatment of pepper and melon plant seeds. An analysis of the discharge and its products revealed the influence of the seeds inserted into the plasma on the total plasma power and concentration of O-3 and NOx, which are the dominant reactive oxygen and nitrogen species produced by the plasma. The plasma treatment of the seeds led to higher viability and higher imbibition rate during the first hour of exposure to the wet environment. X-ray photoelectron spectroscopy (XPS) analysis confirmed changes in the O:C ratio for plasma-treated pepper and melon seeds. However, prolonged plasma treatment for 300 s affected pepper and melon seeds differently. While the O:C ratio gradually increased with plasma treatment time for pepper seeds, that for melon seeds decreased considerably for longer treatment times. Furthermore, detailed XPS analysis of pepper seeds revealed a profound increase in magnesium and calcium, which are often present in seed macronutrients, and a minor increase in potassium, silicon, sulfur, and phosphorus, which are present in micronutrients. These observations can be related to the possible redistribution of the elements owing to the plasma treatment, and thus the treatment might have an essential influence on the seed bulk. The findings presented in this study help elucidate the plasma interaction with surfaces of pepper and melon seeds and confirm the feasibility of the direct plasma treatment using power-modulated DBDs for applications in agriculture.