| Plant has developed adaptive mechanisms to protect themselves against disease and mechinary damages, which may be the same way as suffering other stress when not only physiological and biochemical responses occurs but also a series of physical change is produced. The responses can promote the healing of wound in one hand and induce systemic reactions to hinder the development of damages on the other. Impact injury can open the pathways of pathogenic attack and is one of the most important causes for mould rot. The manual inspection of apples which are among the wounded or diseased ones requires a lot of manpower and money, and this method not only delays the time of warehousing but also bring the fruit secondary damage. At present, rapid diagnosis of mechinary damages and disease have focused on non-destructive research. Moreover, jasmonic acid (JA) is a key signaling component attracted more and more attention recently.Fuji apples harvested from Baishui basis, apple research centre of NWSUAF were empolyed in this study. Dielectric properties were determined in the fruit with red-dot disease, superficial scald and falling wound from a height of 40 cm and 70 cm onto a smooth marble floor. Wounded fruit were stored at room temperature (20±1℃) for 48 h and the effect of impact injury on physiological-biochemi properties and endogenous signaling components was analyzed by using methodology of grey system theory, physiological-biochemi determination and dielectric parameters measurement with LCR electronic instrument. The general goal of this study were:1) to prove the feasibility of using electrical parameters to evaluate disease and inpact injury.2) to establish the mathematical model for correlating multifactor dynamic changes of apple quality to reveal the physiological-biochemi mechanism and the dielectrical properties of pathogenetic and wounded fruits. This will provide some experimental evidences for elucidating the response mechanism of dielectrical properties of postharvest fruit and modifying the theory of wound-inducible signal transduction. It also establish some theoretical basis for developing new non-destructive method and exploiting new non-destructive inspecting instrument. The results were as follows:1. The relationships among the 14 electrical parameters in Fuji apples stored at room temperature for 48h were investigated. Applying LCR electronic measure instrument, the electrical parameters including impedance (Z), admittance (Y), impedance phase angle (0), static capacitance in series equivalent circuit mode (Cs), static capacitance in parallel equivalent circuit mode (Cp), loss coefficient (D or tanδ), inductance in series equivalent circuit mode (Ls), inductance in parallel equivalent circuit mode (Ls), Q factor (Q), effective resistance in series equivalent circuit mode (Rs), effective resistance in parallel equivalent circuit mode (Rp), conductance (G), reactance (X) and susceptance (B) were determined from 100 Hz to 3.98×106Hz at (20±1)℃. The results indicated the reciprocal of Z equaled to Y and the reciprocal of D equaled approximately to Q (f>398 Hz). Moreover, there were significantly positive correlations among Z, X and Lp. This study revealed that it is enough to detect Z,θ, Cp, D, Rp, G and B in future research.2. The dielectric properties in Fuji apples with red-dot disease stored 70 days at (20±1)℃were investigated. Applying LCR electronic measure instrument, the dielectric properties including Z, Lp and X were determined at 100 Hz,1 kHz,10 kHz,100 kHz and 1 MHz. The results indicated thatε', Z, X and Lp for all fruits decreased with increasing frequency. Moreover, there were significantly positive correlations among Z, X and Lp, tanδandε' were significant difference (P＜0.05), but Z, X and Lp were no significance (P>0.05) between diseased and normal fruits from 100 Hz to 1 MHz. Conclusively, tanδandε'can reflect the fruits quality.3. Z, X, G, Cp and D in Fuji apple with superficial scald stored at (20±1)℃were determined from 100Hz to 3.98MHz applying LCR electronic measure instrument. The results showed with increasing frequency, Z and X decreased, Cp and D changed irregularly and G increased in spiral form under same storage times. There was a significantly positive correlation between Z and X and Cp was significant difference (P＜0.01) between diseased and normal fruits from 100Hz to 3.98MHz. In general, Cp was an indicator to pick out diseased fruits.4. The apples fell from a height of 40 cm and 70 cm onto a smoothly marble floor were observed to explore the effects of impact injury on fruit dielectric properties in Fuji apples. The dielectric properties were determined from 100 Hz to 3.98 MHz at (20±1)℃applying LCR electronic measure instrument. There was a significantly negative correlation between Z and B and the absolute value of G is equal to Rp (|G|=Rp). Moreover, Cp and Z were significant difference (P＜0.01) between wounded and sound fruits from 100 Hz to 3.98 MHz at the same stored days. It was concluded that Cp and Z can assess injury status of apples and the optimal frequency was 10 KHz to distinguish wounded and sound fruits.5. The apples fell from a height of 40 cm and 70 cm onto a smoothly marble floor within 48 hours at room temperature were surveyed to investigate the effects of impact injury on fruit quality and activities of protective enzymes in Fuji apples. The results showed that respiration intensity increased significantly, ethylene release rate, O2- production rate and H2O2 content enhanced strongly, the activities of protective enzymes including supiroxide dismutase (SOD), catalase (CAT), peroxidase (POD) and phenylalanine ammonia lyase (PAL) also increased significantly. In Conclusion, impact injury caused membrane-lipid peroxidation of fruits and injury and senescence were induced further. What is more, impact injury can increase the respiration intensity and ethylene release rate and intensify the metabolism of reaction oxidative species (ROS) so that strengthen the induced resistance resulting in promote wound healing and hinder its development in a short time.6. The apples fell from a height of 40 cm and 70 cm onto a smoothly marble floor were explored to investigate the effects of impact injury on endogenous signaling components and activities of lipoxygenase (LOX) in Fuji apples, the contents of JA, salicylic acid (SA), abscisic acid (ABA), nitric oxide (NO), ethylene (Eth) and LOX were detected within 48 hours at room temperature. The results showed that JA content increased significantly, activities of LOX, ethylene production and ABA content enhanced strongly, but NO content decreased. The peak value of JA content preceded the peak value of ABA, and the increasing range of ethylene production was far less than that of JA. The content of bound SA, free SA and total SA decreased sharply and reduced over 70% in a short time. As a result, the highest value of JA contents and the lowest value of free SA contents appeared simultaneously.7. Physicochemical properties and dielectric properties of apples which fell from a height of 70 cm onto a smooth marble floor were determined simultaneously within 48 h and the relationship between them was probed using the methodology of Gray relevancy analysis. Physicochemical property indexes affected diversely dielectric ones. The mathematical model of the dynamic changes of multifactor of apple quality was established using GM (1,6), which can report the effects of various physicochemical property indexes on dielectric ones,. Furthermore, the relationship between dielectric properties and physicochemical properties was uncovered by GM (1,2). It was concluded that TSS can be described by Cp and Rp, TA can be described by Rp. GM (1,1) used to estimate the dynamic change regularity of deg and Cp was established. The feasility of the model was proved by practice test. The results indicated that it was feasible to determine and estimate the fruit quality using electrical parameters, which was significant and useful in both theory and practice.
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