Gliding Arc Plasma Treatment of Maize (Zea mays L.) Grains Promotes Seed Germination and Early Growth, Affecting Hormone Pools, but Not Significantly Photosynthetic Parameters

Maize grains (Zea mays convar. Indentata Sturt.) were treated with non-thermal plasma, where Gliding Arc plasma discharge at an atmospheric pressure was used (working gas: Air; time duration: 0 s, 180 s, 300 s, 600 s). The experiment was conducted at a temperature of 18 °C, light/dark 12/12 h, and a light intensity of 100 µmol/m2s. Seed germination, seedling growth, photosynthetic parameters, and hormone (abscisic acid, jasmonic acid, salicylic acid, indole-3-acetic acid, and cytokinin) contents were measured. The highest stimulation of seed germination (to 141%), root length (to 221%), shoot length (to 298%), and root weight (to 122%) in comparison with the control was recorded after Gliding Arc plasma treatment for 600 s. The photochemical and non-photochemical Chl fluorescence parameters were not significantly affected by Gliding Arc plasma treatment. In contrast, hormonal pools in maize were significantly affected. The short-term plasma treatment (180 s) was associated with a decrease in the stress hormones abscisic acid, salicylic acid, jasmonic acid, and jasmonate isoleucine, while indole-3-acetic acid and cytokinin precursors were elevated. Longer-term treatment (300 s, 600 s) had an opposite effect—an elevation of abscisic acid, jasmonic acid, and jasmonate isoleucine as well as active cytokinins. The content of auxin decreased. Gliding plasma treatment may significantly affect maize physiology, dependent on the treatment duration.