Studies On Mechanism Of Inducing Chilling Tolerance By Heat Shock Treatment In Green Peppers

In order to study the approaches to reduce chilling injury, green peppers were treated by postharvest heat shock treatment at at45℃for4min or at50℃for1min, the chilling injury and the mechanism of inducing chilling tolerance by heat shock treatment were focus on.The experiments observed physiological changes and torage characteristics,studied the metabolization of active oxygen and lipid peroxidation, measured the changes of cell wall components and protein synthesization.1、Green peppers were climacteric vegetable becausethey had a respiration peak during the cold storage.2、The fruits stored at2℃had slight chilling injury symptom only after2weeks and suffered severe chilling injury when the storage duration surpassed4weeks with significant loss of Vc, chlorophyll, soluble protein。The chilling injury index reached86.5%at the end of storage. Low temperature stress increased respiration rate greatly and decreased ability of chilling tolerance in green peppers.3、It was low temperature that stimulated the increment of H2O2and O2-, enhanced the activity of LOX which started membrane lipid peroxidation, inhibited active oxygen scavenging and SOD and CAT, POD worked unbalanced, MDA content and membrane relative permeability increased during storage which resulted in membrane structural damage and the occurrences of chilling injury of green peppers.4Heat shock treatment inhibited chilling injury occurrence and development, maintained high level of Vc content, reduced in cumulation of MDA content, retarded increase in membrane permeability and decrease in chlorophyll and protected the stability of membrane.That were45℃,4min and50℃,1min which induced chilling tolerance of peppers best and the rate of good results was still80%or76.5%as the cold storage peppers extend by the50days’.5、The results indicated that heat shock treatment induced the increase of endogenous H2O2content in the beginning of storage, reduced the injury index and O2-formation rate, enhanced the activities of SOD, CAT and APX and postponed the decrease of AsA content, resulting in inhibiting the accumulation of O2-and MDA and increase in LOX activity In the late of storage. Heat shock treatment may maintain the balance between the formation and detoxification of active oxygen species and delay the lipid peroxidation process, thereby preventing the development of chilling injury of cold-stored green peppers.6、A new heat-stable protein peppers which was induced by heat shock treatment improve the chilling tolerance of green peppers. Heat shock treatment significantly delayed the respiration peak, inhibited respiration intensity and activity of PG and Cx, slow down the degradation of original pectin and cellulose, avoided cell wall metabolism abnormally caused by low temperature stress and reduced the symptoms of chilling injury of green peppers.