The changes of chlorophyll fluorescence parameters of Echinacea purpurea after pre-sowing seed treatment with cold plasma

Abstract

The pre-sowing seed treatment with cold plasma (CP) is currently used in the field of agricultural science as an alternative technology for improving agricultural performance of crops. Seed exposure to CP can lead to stimulation of germination and seedling development followed by the long-term changes in plant metabolism. The objective of this study was to evaluate the persistence of effects of pre-sowing seed treatment with CP on physiological and biochemical activity of plants by chlorophyll a fluorescence parameters in leaves perennial medicinal plant purple coneflower (Echinacea purpurea) in the second season of vegetation. Seeds were processed with capacitively coupled plasma device at a pressure of 60 Pa. The duration of CP exposure was 2, 5 and 7 min. Seeds were sown to substrate four days after CP treatment and seedlings grown for two vegetation seasons. At the beginning of flowering growth stage during the second vegetation season, the chlorophyll a fluorescence measurements were performed by a Plant Efficiency Analyser (PEA) with randomly selected youngest fully expanded leaves. The results showed, that CP had statistically significant effect on several fluorescence parameters of E. purpurea even in the second year after treatment. The differences in the efficiency of second photosystem (Fv/Fm) between control and treated groups were statistically significant (p<0.05): this parameter was higher by 14.7, 13.5 and 14.3 % after 2, 5 and 7 min CP treatments, respectively. Electron transport flux per reaction center (ETo/RC) was also higher for plants grown from CP treated seeds. E.g., seed exposure to CP for 7 min resulted in 47.9% (p<0.05) increase of ETo/RC. The increase of electron transport and efficiency of the PSII might be explained by more than 50 % (p<0.05) decreased dissipated energy flux per reaction center (DIo/RC) after CP treatment. [...]