LAUSR

The electrical impedance spectra of fresh and naturally aging rice seeds were measured to develop a non-destructive method for measuring the vigour of such seeds. To this end, three frequencies were selected using the coefficient of variation method within various frequency domains. A prediction model was then established using Fisher linear discriminant analysis, with the impedance, phase angle, and three-dimensional size of the seeds at the selected frequencies as independent variables and fresh and aging seeds as dependent variables. The water states and micromorphology of the seeds were subsequently evaluated to reveal the influence mechanism of impedance and vigour. The results showed that the impedance parameters of fresh and aging seeds were distinguishable, and the difference was evident in the low-frequency region. Moreover, the discriminant analysis model showed good predictive ability; the accuracies of the discriminant functions, Y1 and Y5, were 90%. The impedance variables had a significant influence on the accuracy of the model, and the prediction accuracies for the fresh and aging seeds were improved by 24% and 14%, respectively, through introduction of the independent variables. Additionally, changes in the vigour, water state, and impedance were observed to be interrelated. The moisture content of the aging seeds was mainly affected by the content of bound water, and the ratio of bound water was inversely proportional to the impedance value. The variation in the impedance of the aging seeds was deemed to result from the combined effect of water state and micromorphology.