[INVITED] The response of perennial plants to pre-sowing seed treatment with low-temperature plasma: results of long-term observations

The response of plants to seed treatment with low temperature plasma (cold plasma, CP) was extensively studied and numerous studies reported that improved seed germination and seedling growth can be achieved for a large variety of annual plants. We chose perennial species for investigation with the intention to perform longer-term observations. We report the results of long-term (at least two vegetation seasons) observations of experiments performed on 3 perennial woody species (black mulberry, Morus nigra L.; Smirnov’s rhododendron, Rhododendron smirnowii Trautv.; Norway spruce, Picea abies) and 2 perennial medicinal plants (purple coneflower, Echinacea purpurea (L.) Moench; red clover, Trifolium pratense L.). The results indicate that response of perennial plants to seed treatment with CP is dependent on plant species, seed dormancy state, and the duration of seed storage but the resulting effects on seedling development can be several fold stronger in comparison to those reported for annual plants. Longer-term observations revealed that the effects persisted for more than a year for all studied plant species. For all three studied wooden plant species, plants grown from seeds characterized by the negative effects of CP treatments on germination and early growth, in end of the second vegetation season performed substantially better – developed more leaves and branches, had greater total leaf surface area, larger height than the control plants (e.g., the mean total leaf surface area per plant for Smirnov’s rhododendron was up to 16-fold larger; Norway spuce seedlings grown from CP treated seeds, had 50-60% larger height and 40-50% increased branching in comparison to the control seedlings). CP treatments improved germination and early growth of medicinal plants – purple coneflower and two cultivars of red clover. CP treatment induced positive changes in morphometric traits of both medicinal plants studied (height, branching, leaf number, root weight) observable at least two vegetation seasons. In both medicinal plants seed treatment with CP induces significant changes in pharmaceutically important secondary metabolite content. The amount of cichoric acid per plant of purple coneflower was increased up to 3.8fold, and amount of vitamin C – up to 1.9 fold. Similar finding was obtained with red clover: the amount and ratio of isoflavones formononetine and biochanine A in leaf extracts was substantially changed by pre-sowing seed treatment with CP. These results suggest that commonly used estimates of stressor effects, such as germination rate or seedling morphology, are not sufficient to define the stress response, at least for perennials. 第78回応用物理学会秋季学術講演会 講演予稿集 (2017 福岡国際会議場) 5p-S22-1