Black locust (Fabaceae family) seeds are known for their strong dormant state and are an excellent candidate for studying and developing methods to break dormancy. We investigated overcoming the dormancy using several different sources of non-thermal plasma, which, by modifying, etching, or disrupting the waxy seed coat, allowed water to penetrate the seeds and initiate germination. All plasma sources tested enhanced seed germination to varying degrees, with over 80% germination observed when using a dielectric barrier discharge, while control seeds showed no germination. Non-thermal plasma treatment significantly decreased the water contact angle of the seed surface from an initial 120° (for untreated seeds) to complete wetting when using a dielectric barrier discharge or atmospheric-pressure plasma jet. The experiments indicate two mechanisms for the modification of the waxy seed coat by a non-thermal plasma: hydrophilization of the wax surface through the binding of oxygen particles and etching of narrow channels in the wax layer, allowing water to penetrate the seed.

• Keywords
• Robinia pseudoacacia, black locust, non-thermal plasma, seed dormancy, seed germination, seed treatment,
• Publication type
• Journal Article MeSH

The paper reports a low-cost handheld source of a cold air plasma intended for biomedical applications that can be made by anyone (detailed technical information and a step-by-step guide for creating the NTP source are provided). The plasma source employs a 1.4 W corona discharge in the needle-to-cone electrode configuration and is an extremely simple device, consisting basically of two electrodes and a cheap power supply. To achieve the best bactericidal effect, the plasma source has been optimized on Escherichia coli. The bactericidal ability of the plasma source was further tested on a wide range of microorganisms: Staphylococcus aureus as a representative of gram-positive bacteria, Pseudomonas aeruginosa as gram-negative bacteria, Candida albicans as yeasts, Trichophyton interdigitale as microfungi, and Deinococcus radiodurans as a representative of extremophilic bacteria resistant to many DNA-damaging agents, including ultraviolet and ionizing radiation. The testing showed that the plasma source inactivates all the microorganisms tested in several minutes (up to 105-107 CFU depending on a microorganism), proving its effectiveness against a wide spectrum of pathogens, in particular microfungi, yeasts, gram-positive and gram-negative bacteria. Studies of long-lived reactive species such as ozone, nitrogen oxides, hydrogen peroxide, nitrite, and nitrate revealed a strong correlation between ozone and the bactericidal effect, indicating that the bactericidal effect should generally be attributed to reactive oxygen species. This is the first comprehensive study of the bactericidal effect of a corona discharge in air and the formation of long-lived reactive species by the discharge, depending on both the interelectrode distance and the discharge current.

• Keywords
• Bactericidal effect, Cold air plasma, Corona discharge, Ion wind, Reactive oxygen and nitrogen species,
• MeSH
• Anti-Bacterial Agents pharmacology   MeSH
• Candida albicans drug effects   MeSH
• Escherichia coli drug effects   MeSH
• Plasma Gases * pharmacology   MeSH
• Staphylococcus aureus drug effects   MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Anti-Bacterial Agents MeSH
• Plasma Gases * MeSH