Preservation effect of cut Phalaenopsis by low voltage electrostatic field (LVEF)

This study aims to explore the effect of low voltage electrostatic field (LVEF) treatment on the preservation of cut Phalaenopsis. The cut Phalaenopsis "Paradise Bird" was treated by LVEF (test group) and without LVEF treatment (control group) in the vase period. The indexes were evaluated, including the fresh weight, flower diameter, soluble sugar content, soluble protein content, relative conductivity, malondialdehyde (MDA) content, and related antioxidant enzyme activities (SOD, POD, and CAT) of cut Phalaenopsis. A systematic analysis was implemented on the water migration and water loss of cut Phalaenopsis during the vase period. The content of the water phase was determined using low-field nuclear magnetic resonance (LF-NMR). The water distribution in the cut Phalaenopsis was also observed by MRI pseudo-color imaging. Firstly, the experimental objects were selected as the cut Phalaenopsis with good freshness, and smooth flower surface without the pests and mechanical damage. The cut Phalaenopsis were randomly divided into two groups. The cut Phalaenopsis was frozen at low temperature (without LVEF) as the control group, while the cut Phalaenopsis was treated with LVEF as the test group. Both groups were then stored at (4±1) ℃. The results showed that the cut Phalaenopsis treated by LVEF maintained a better appearance, compared with the control group. Among them, the fresh weight and flower diameter increased by 4.88 % and 4.98 %, respectively, and the content of soluble sugar and soluble protein increased by 0.75 and 4.09 mg/g, respectively. At the same time, the cell membrane permeability of cut Phalaenopsis was also maintained after LVEF treatment. The membrane lipid peroxidation was slowed down to improve the activity of antioxidant enzymes. The relative conductivity and MDA content also decreased by 31.53 % and 21.96 nmol/g, respectively. Furthermore, the LVEF treatment also improved the activity of related antioxidant enzymes. Among them, the peak levels of SOD, POD, and CAT increased by 19.58, 20.77, and 20.21 U/g, respectively. The water phase state of LF-NMR showed that there was a slower decrease in the peak area ratio of cut Phalaenopsis treated by LVEF treatment, compared with the control group. The LVEF treatment also delayed the change of water migration and water loss of cut Phalaenopsis. The MRI pseudo-color imaging results show that the petals of the control group seriously shrunk and wilted by 28 d. Therefore, the LVEF treatment improved the fresh weight and flower diameter of cut Phalaenopsis, whereas, the loss of soluble sugar and soluble protein content was reduced during the vase period. There was a delay increase in the relative conductivity and MDA content of cut Phalaenopsis. The activity of related antioxidant enzymes was also improved to delay the water migration and water loss of cut Phalaenopsis. Therefore, the LVEF treatment can effectively enhance the ornamental quality to delay the senescence of cut Phalaenopsis. The great potential of LVEF preservation can be gained in commercial utilization, particularly in the cut flower preservation market. The finding can also provide the theoretical basis and technical reference for the application of cut Phalaenopsis.