Biological Effects Of Seeds Treated With High Voltage Corona Discharge Field

As a new physical agricultural treatment technology,high voltage corona discharge field has been paid more and more attention by experts and scholars at home and abroad because of its advantages such as simple equipment,obvious biological effect and environmental friendless.Analysis of the physical characteristics of the high voltage corona discharge field,the biological effect of the high voltage corona discharge field is mainly caused by two factors,one is the high voltage non-uniform electric field,the other is the active substance of the discharge plasma.In order to explore the respective effects and contributions of the two main factors in the high voltage corona discharge field,that is,the non-uniform electric field and the discharge plasma.In this study,alternating current(AC)high voltage multi-needle-plate corona discharge field was used to treat naked oat seeds and direct current(DC)high voltage multi-needle-plate corona discharge field was used to treat Ammopiptanthus mongolicus seeds.Each treatment was divided into two groups:one group was exposed directly,and the other group was treated with petri dish cover to block ion wind etching,which could be approximately the single factor effect of non-uniform electric field.The results showed that:In the experiment of treating naked oat seeds with AC high voltage corona discharge field,except for the 8kV treatment group,the water absorption of seeds in other treatment groups increased to varying degrees.The etching degree of naked oat seed coat and the fresh weight of seedlings showed an upward trend with the increase of voltage,while the reactive oxygen species(ROS)content of seedlings decreased.The ion wind speed on the seed surface was zero when the petri dish cover was added.At the same time,the Scanning Electron Microscope(SEM)results showed that the etching degree of the direct exposure group was more serious than that of the covered group,indicating that the combined effect of the ion wind and the non-uniform electric field had a greater impact on the microscopic morphology of the seed coat.Fourier Transform infrared spectroscopy(FTIR)results showed that high voltage corona discharge field treatment could increase the content of hydrophilic substances in seed coat,cellulose degradation,reduce the content of hydrophobic substances such as wax,and increase the hydrophilicity of seeds.The study found that most of the high voltage corona discharge field treatment groups can form a new absorption peak at 1740 cm^-1,which is closely related to the hydrophilicity of the seeds.Regardless of whether it is covered or not,the high voltage corona discharge field treatment can improve the hydrophilicity of the seed.The cover of the petri dish can reduce the etching degree of the seed coat,but increase the hydrophilicity of the seed,indicating that the non-uniform electric field has a greater impact on the hydrophilicity of the seed.In the experiment of treating Ammopiptanthus mongolicus seeds with DC high voltage corona discharge field,the surface of the seed coat of Ammopiptanthus mongolicus treated with corona discharge has wind erosion morphology,many small gullies were produced,and the seed coat surface cracked serious.Fourier transform infrared spectroscopy showed that the corona discharge plasma treatment of Ammopiptanthus mongolicus had increased vibration at 3412 cm^-1?1739 cm^-1?1628 cm^-1?1429 cm^-1?1334 cm^-1?1160 cm^-1?1051cm^-1,indicating that the hydrophilic functional groups increased and the corona discharge could change the chemical composition of Ammopiptanthus mongolicus seed coat.The apparent contact angle of the seed coat of Ammopiptanthus mongolicus decreased significantly from 99.82±4.86°before treatment to 60.11±8.44°,indicating that corona discharge can significantly improve the hydrophilicity of Ammopiptanthus mongolicus seeds.Compared with the control group,the water absorption of the seeds after the high voltage corona discharge field treatment increased to varying degrees.All the treatment groups had seeds germinated at 24 h,while the control group had zero germination.It showed that high voltage corona discharge field treatment can significantly affect the seed coat structure and properties of Ammopiptanthus mongolicus,improve the hydrophilicity and water absorption of the seeds,and promote the germination and growth of Ammopiptanthus mongolicus seeds.Comprehensive analysis shows that under the same voltage,the electric field irradiation intensity of the seeds in the DC corona discharge field is greater than that in the AC corona discharge field.In AC and DC corona discharge fields,the ion wind speed of the direct exposure group increased with the increase of the voltage,and the ion wind speed in the DC high voltage corona discharge field is greater than that of the AC high voltage corona discharge field.Both the ion wind and the non-uniform electric field can improve the hydrophilicity and water absorption of naked oats and Ammopiptanthus mongolicus seeds,and in terms of hydrophilicity,the non-uniform electric field in the AC corona discharge field has a greater impact on the hydrophilicity of naked oat seeds,while the combined effect of the ion wind and the non-uniform electric field in the DC corona discharge field has a greater impact on the hydrophilicity of Ammopiptanthus mongolicus seeds.Both high voltage corona discharge fields can etch the coats of these two planted species,and the degree of seed coat etching increases with the increase of voltage.The direct exposure group was more severely etched than the covered group,indicating that the combined effect of the ion wind and the non-uniform electric field had a greater impact on the microscopic morphology of the seed coat.The cover of the petri dish can effectively reduce the physical etching degree of the seed by the discharge plasma,at the same time reduce the field strength received by the seed,and make the radiation electric field received by the seed more uniform.Regardless of whether it is covered or not,the high voltage corona discharge field can change the chemical composition of the seed coat,thereby improving the hydrophilicity of the seed.With the increase of discharge voltage,the chemical composition of seed coat changed more,and the etching of seed coat increased,the hydrophilic substances in seed coat increased,cellulose degradation and surface cracks increased,which improved the water absorption and permeability of seeds.Mild and moderate electric field stimulation can increase enzyme activity,accelerate the formation of new cells,increase seed vigor,and promote root bud differentiation and growth,thereby promoting the height and fresh weight of seedlings after high voltage corona discharge field treatment.From the macroscopic effect,the effect of DC corona discharge is better.This research provides experimental data support for the analysis of surface modification and chemical composition of seeds treated by high voltage corona discharge field,and provides ideas for revealing the biological effect mechanism of high voltage corona discharge field.