Enhancement Propagation of Protocorms in Orchid ( Cymbidium tracyanum L. Castle) by Cold Atmospheric Pressure Air Plasma Jet

Propagation of orchid (Cymbidium tracyanum L. Castle) treated by using an air cold atmospheric pressure plasma jet at room temperature was investigated. The peak-to-peak voltage discharge and flow rate of the air atmospheric pressure plasma jet were set at 10.5 kV and 10 L/min, respectively. The constituent particles of the air cold atmospheric pressure plasma jet were revealed by optical emission spectroscopy. At the end of the jet nozzle, the constituent particles were observed, such as hydroxyl radical ˙OH, N2 first negative system (N2 1 −), N2s positive system (N2 2 +), and atomic oxygen. The average size, average number of buds, fresh and dry weights simultaneously increased by cold air plasma treatment compared with the control ones. The highest positive effects of treated protocorms on average size, average number of buds, fresh and dry weight were significantly improved by 238.2, 475.9, 85.6, and 152.5%, respectively. The transmission electron microscope showed the cytoplasmic cell wall in orchid protocorm disturbed by air cold plasma. Thus, the effects of constituent particles of air plasma might attack in the cell wall of protocorm leading to cell loosening, which improved elongation and released bud dormancy. These results indicated that the propagation of orchid protocorms depended on the effects of air cold plasma treatment with different plasma time durations.