Abstract: The invention comprises an apparatus, method and system used to treat various liquids, seeds, and soil or other growth media used in cultivating plants by exposure to a plasma discharge. The system comprises a novel electrode structure which utilizes a tapered inner electrode and a porous outer electrode to create a three-dimensional plasma discharge, which is applied to liquid, seeds or growth media through removably attachable sub-assemblies. When used to treat water or seeds, highly-concentrated plasma activated water (PAW) and disease and drought resistant plasma activated seeds (PAS), respectively, are produced, which improve germination rate and efficiency, and eliminate the need for ammonia-based chemical fertilizers.