Effect of corona discharge field processing on vigor of three layers of paddy seeds

Abstract: In order to increase the efficiency of a corona discharge field processing aged paddy seeds, a positive pulse corona discharged field consisting of an arc-shaped prick electrode array and a plate electrode (as the grounding electrode) was developed in this research. The gap between the arc-shaped electrode array and the plate was 50 mm. After adjusted with an AC transformer and converted into the positive pulse DC voltage with a diode (a half-wave rectifier), the positive pulse high voltage was supplied to the arc-shaped electrode array, it was 18 kV, 20 kV and 22 kV (RMS), respectively. The treatment time was 4 min. The effect of the corona discharge field on the vitality index of 3-layer of the aged paddy seed laid on the plate electrode was explored. The seeds were separated with a plastic gauze. The results showed that the positive pulse corona discharged field had the different effects on the vitality index of the paddy seeds laid on the different positions at the same processing voltage and time. It was found that the four vitality indexes (the germination potential, germination rate, germination index and vigor index) of the upper layer paddy seeds had been significantly improved (P <0.01 or P <0.05) in comparison with the untreated samples at 18 kV (RSM), however, the four vitality indexes of the middle and the lower layers were not significantly different from that of the CK. The four indexes of all treated samples at 20 kV (RSM) were significantly increased in comparison with that of the CK (P <0.01 or p<0.05), in addition, there were no differences between the different layer samples (P>0.05). The germination rate, germination index and vigor index of the lower layer paddy seeds at 22 kV (RSM) were significantly higher than that of the CK (P <0.01 or P <0.05), but the vitality indexes of the upper and the middle layer paddy seeds had no significant differences in comparison with that of the CK. It was also found that the germination peak numbers of the upper layer seeds at 18 kV (RMS), all layer seeds at 20 kV (RMS), and both of the middle and lower layer seeds at 22 kV (RMS) appeared one day in advance during germination. This results were consistent with the improvement of the vitality indexes. The results showed that the corona discharge field for processing the multi-layer seeds to increase seed vitality index was feasible. However, the treatment energy supplied to seeds by a corona discharge field should be in an optimum range, it means that there is an optimum treatment condition, including the electric field strength and processing time. The mechanism of a corona discharge field improving the germination of seed perhaps is resulted in the reorientation and rearrangement of the membrane components in dry seed during processed with an electric field, but it should be further researched.