Biological Effects Of Alfalfa Treated With High-voltage Corona Discharge Field

High-voltage corona discharge field biological mutagenesis technology is a physical mutagenesis technology with simple device,evident biological effect,and environmental friendliness.In order to study the biological effects of high-voltage corona discharge field treatment on alfalfa,especially the effects of two factors on the seeds:non-uniform electric field and plasma injection caused by corona discharge,an AC high-voltage needle-plate corona discharge field with a frequency of 50 Hz,a distance from the tip of the electrode to the grounding end of 4 cm,and a voltage of 0（CK）,4 k V,8 k V,12 k V,16 k V,19 k V was used to treat alfalfa seeds at atmospheric pressure for 30 minutes,alfalfa seed were divided into two groups,one group was covered with 1 mm-thick polypropylene petri dish cover that can be approximated as a single factor effect of non-uniform electric field,the other group was directly irradiated by corona discharge field under different parameters.The apparent contact angle of the alfalfa seed coat before and after treatment with corona discharge field was tested,and it was found that the apparent contact angle of the seed when untreated was 128.39±1.09°,which was much greater than 90°and showed hydrophobicity.After treatment,the apparent contact angle of the seeds dropped sharply,and the 19 k V non-covered group dropped to 74.74±10.42°.The treatment group showed the largest change in hydrophilicity.Scanning electron microscopy results showed that the microstructure of the untreated seed coat can clearly observe that the cap-shaped protrusions are interconnected to form a network structure and its boundary,and the boundary of the surface network structure becomes blurred after the corona discharge field treatment.The non-covered treatment group changed more greatly,and its surface cap-shaped protrusions became thinner or even disappeared,and a large number of fine grooves appeared.Among them,the 19 k V non-covered treatment group had the largest change.Fourier transform infrared spectroscopy（FTIR）and dual-index sequence analysis were used to detect and compare the spectra of alfalfa seed coats with different treatments.Based on the infrared fingerprint of the alfalfa seed coat,the common peak ratio and the variable peak ratio of the measured samples were calculated and the clustering analysis was performed using a dual-index sequence.Results showed that the peaks of the seed coat at 2856 and 1727 cm^-1in the treatment group changed,indicating that hydrophobic wax,lipid,and cellulose may be cracked or degraded.Corona discharge field treatment can change the chemical structure of alfalfa seed coats,resulting in the changes in their hydrophilicity.After treatment,the effects of different parameters on the growth characteristics of alfalfa seeds,such as germination potential,germination rate,seedling height,fresh weight,water absorption,and conductivity of the seed extracts,were examined.The results show that when alfalfa seeds were treated with the corona discharge field,the presence or absence of a petri dish cover had a completely opposite effect on the germination potential and germination rate of alfalfa seeds.The overall change trend was a non-monotonic oscillation curve;the absorption rate of each group increased compared with the control,except for the 8 k V covered group.The corona discharge plasma not only has a direct effect on seeds,but also may generate free radicals including active oxygen to damage the organism.Active oxygen is an important marker connecting the physical and biological interpretations of the original role of the electromagnetic causal chain.After the inoculation,the reactive oxygen species content of the seedlings was measured.As a result,compared with the control group,the active oxygen content of the treatment group increased with time and then decreased.The results were found by combining all the test indicators that the petri dish cover can effectively reduce the physicochemical etching of ionic wind,the hydrophilicity of alfalfa seeds improved after corona discharge field treatment regardless of whether there is an ionic effect during irradiation,and the ionic wind has a greater influence on the hydrophilicity of alfalfa seeds than the non-uniform electric field.With the increase of the voltage,the alfalfa seed coat was severely etched,the degradation of the seed epidermal cellulose and the increase of cracks on the surface of the seed coat led to the improvement of its water absorption capacity,and further improved the growth characteristics such as seedling height.And under mild to moderate stimuli,a stress response was generated in the plant,enzyme activity was enhanced,osmotic adjustment ability was enhanced,new cells were accelerated to promote plant growth,and the effects of high-voltage corona discharge field treatment had been transformed into macro biological effects.This study provides ideas and experimental evidence for expanding the research field of high-voltage corona discharge field biotechnology,and provides experimental data support for the research of high-voltage corona discharge field biotechnology mechanism.