Plasma agriculture has been considered as a promising solution for sustainable and safe agri-food production. Its applications include germination induction, plant-growth stimulation, post-harvest sterilization and management. For growth stimulation, both direct and indirect applications have been widely studied. For indirect plasma application, plasma-activated medium has largely been tested for its uses in plant management. This study preliminarily reports the diffusion pattern of plasma active radicals in semi-solid model and its effects on bacterial killing and plant tissue culture. A pulsed plasma jet with feeding gases of artificial air, ambient air, , , and was used in this study. Results showed the generation and the deposition of inorganic ions of nitrogen––nitrate and ammonium––in the agar gel. Effects of feeding gases, medium softness, gas flow rate and activated-medium storage time on bacterial sterilization were also examined using Escherichia coli culture. The -treated medium showed the antimicrobial effects lasted for at least 60 min after the exposure. The distribution of RONS in the medium was visually examined by KI-starch chromogenic reaction and showed results relevant to the bactericidal effects. Effects of indirect plasma treatment on tissue culture shoot multiplication were also examined. Taken together, these results suggest that -treated media are a promising solution that can be widely used for economically important plant tissue cultures. Supplementary Information The online version contains supplementary material available at 10.1007/s11090-022-10228-4.