| Responding mechanisms of'Fuyu'(Diospyros kaki. L. cv.'Fuyu') non-astringent persimmon, one of the varieties mainly grown in China, to different storage temperature (20±2℃and 0℃±2℃) and 0.5μL·L-11-MCP treatment in the process of fruit softening, were systematically studied through examining changes of the active oxygen metabolism, ethylene metabolism, fruit quality, composition and cell wall ultrastructure based on the dialectical relation between structure and function. The variation rules of electrical properties of non-astringent persimmon were also synchronously measured by using electronic instrument of Inductance Capacitance Resistance (LCR). The main results are shown as following:1. Low temperature treatment can significantly inhibit respiratory rate, ethylene metabolism, active oxygen metabolism, membranous peroxide of'Fuyu'Non-astringent persimmon fruit and delay the fruit softening process in postharvest storage period. However, the Non-astringent persimmon fruit is'cold sensitive', and easy to occur chilling injury such as total polyphenol content and browning increasing. 1-MCP treatment can inhibited the respiratory rate and ethylene production rate to some extent and significantly reduce the fruit chilling injuries during the storage period.2. Trough inhibiting the activity of ACS, the key enzymes in ethylene synthesis, reducing the production of ACC, the catalyzed substrate of ACO, and depressing the activity of ACO, 1-MCP treatment inhibited biosynthesis of ethylene. The rapidly increase of ACS, ACO activity and ACC content of fruit Treating with exogenous ethylene causes rapidly increasing in ACS, ACO activity and ACC content of fruit and is the main reason for the increase of ethylene production at cold storage.3. 1-MCP treatment inhibited the decrease in the activity of the system of scavenging active oxygen activity (Superoxide dismutase/SOD, Peroxidase/POD, Catalase/CAT and Ascorbate peroxidase/APX) and inhibited the increase in the activity of the lipoxygenase (LOX) and accumulation of Malondialdehyde (MDA) content. By reducing the fruit production rate of O 2? and H2O2 content, 1-MCP inhibited lipid peroxidation induced by the ethylene biosynthesis and delayed the senescence of persimmon fruit. The increase of O 2? and the H2O2 content treated with ethylene resulted in disordering of fruits reactive oxygen scavenging system, and accelerating senescence of the fruit at cold storage. 1-MCP treatment decreased of total phenolic content and polyphenol oxidase(PPO) activity, increased polyphenol oxidase(PPO) activity, maintained the cell compartments of the structure, therefore, reduced the browning of fruit chilling injury.4. During room temperature (20±2℃) storage, firstly, the initial xylanase (Xyl) hydrolyzed hemicellulose, then pectin esterase enzyme ( PE ) demethylated the pectin methyl which resulted in Catalytic acid inverting pectin acid ester, produced the substrate suitable for poly-generation for galacturonic acid enzyme (PG), and bound-soluble pectin became water-soluble pectin, that is , the content of water- soluble pectin (WSP ) increased, chelator soluble pectin (CSP), sodium carbonate soluble pectin (SSP) and alkali soluble pectin (ASP) decreased as well, the hydrolysis of cellulase (Cx) shortened a long chain of cellulose cell walls, leading to the final fruit softening. 1-MCP treatment significantly inhibited the activity of Xyl, significantly delayed the enzyme activity increase of PE , PG and Cx in persimmon fruit, and prevented the degradation of hemicellulose, pectin and cellulose, thus postponed the persimmon fruit softening.5. During room temperature (20±2℃) storage, the changes of cell ultrastructure corresponding physiological and biochemical changes of 'Fuyu' persimmon fruit were as following: cell wall kept structural integrity and middle lamella and primary wall tied tightly immediately after harvest; in the fruit softening process, middle lamella degraded and disappeared gradually, the cell wall microfibril structural disordered flocculently and cell plasmolysis occured; the chloroplasts disintegrated gradually and the osmiophilic granules gradually increased in number and size; mitochondrial cristae became illegible; subsequently, cytoplasmic degraded, structural damage to interstitial cells appeared, vacuole rupture and cell wall splited partly. As for 1-MCP treated fruits, recession of pulp tissue cell wall structure was relatively lagging, cell wall, middle lamella, the basic structure of chloroplasts and mitochondria kept integrity. These verify from microscopic viewpoint that 1-MCP treatment maintain the structural integrity of the pulp cells,therefore keep the hardness of persimmon fruit effectively, delay the persimmon fruit softening and aging process and then explain the unity of structure and function.6. With the electronic instrument of LCR, the 11 electrical parameters were carried out in different morphological maturity and postharvest freshness persimmon fruit. The results showed that the electronic parameters had the same electrical requency characteristics. The results also showed that the value of impedance (Z), effective resistance in parallel equivalent circuit mode (Rp), reactance (X) and inductance in parallel equivalent circuit mode (Lp) decreased gradually, the value of conductance (G), susceptance (B) and admittance (Y) increased gradually, and the value of static capacitance in parallel equivalent circuit mode (Cp ), impedance phase angle (θ), loss coefficient (D) and Q factor (Q) changed erratically following the increasing frequency. Therefore, these electrical parameters can be used to examine differences in persimmon fruit maturity and postharvest freshness, so as to achieve the purpose of classification of persimmon fruit. Through statistical analysis, 100 kHz was selected as the best electrical stimulation frequency in differentiating morphological maturity and postharvest freshness of persimmon fruit.7. Under 100 kHz frequencies, the correlation among electrical parameters, fruit weight, diameter, hardness and soluble solids content of persimmon fruit in different morphological maturity were analyzed. The results showed that the fruit maturity and quality, during the development, could be identified based on the changes of Cp, and G, B and Y can also be used as complementary indicators.8. Under 100 kHz frequency electrical stimulation, through the correlation analysis of the electrical parameters associated with the fruit cell wall hydrolase activity, firmness, soluble solids content and ethylene production rate of fruit during storage, Rp, Cp, G, B and Y were screened out as the sensitive electrical parameters to identify Fruit firmness during storage, D,θand Q to identify soluble solids Content.
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