Spectral characteristics on increasing hydrophilicity of Alfalfa seeds treated with alternating current corona discharge field.

In this study, corona discharge at atmospheric pressure under an alternating current (AC) field with a multi-needle plate electrode structure was used as mutagen to study the effects of corona discharge field on the hydrophilicity of alfalfa seeds, especially the effects of non-uniform electric field that is frequently ignored. 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. 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. Results showed that the peaks of the seed coat at 2856 and 1727 cm−1 in 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. The results of the apparent contact angle and scanning electron microscopy (SEM) and other experiments showed that the change in 19 kV non-covered treatment group was greatest, 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. This study revealed the biological effect mechanism of corona discharge field from the perspective of spectral characteristics and provided experimental data support for the analysis of alfalfa seed surface modification and chemical structure after corona discharge field treatment. Unlabelled Image • The contributions of non-uniform electric field and ionic wind on hydrophilicity of seed was studied. • Dual-index sequence analysis was used to compare different treatment groups. • Corona discharge field treatment can improve the hydrophilicity of alfalfa seeds. • IR spectrum results indicate changes in chemical structure of the treatment group. • For hydrophilicity, the contribution of ionic wind is more than nonuniform electric field. [ABSTRACT FROM AUTHOR]