| This research took loquat fruits(Eriobotrya japonica Lindl. cv. Jiefangzhong) as test materials, studying postharvest physiology and quality changes of loquat fruits by hot treatment and its comparison( not hot treatment) under the condition of normal temperature (22-28℃) and low temperature(2-5℃) respectively. by analyzing and determining some varieties of physiology index during cold storage, changes of related enzyme activities and varieties rules of microscopical structure of cell wall, inducing reason and mechanism of inferior phenomenon of loquat fruits and physiological mechanism of hot treatment alleviating chilling injury were discussed during cold storage.Result as followed:Although decay index of loquat fruits were eased under low temperature(2-5℃) obviously,The symptoms of chilling injury during cold storage were appeared at the same time, The performances were adhesive and difficult to peel pericarp,extractable juice rate decrease and hardness increase,and accompanied with excessive water stains and lignification phenomenon of its texture that chilling injury phenomenon occurred during cold storage.It was low temperature that caused respiration rate to go up and stimulated the increment which ethylene synthesized unusually,lignin cumulated abnormally under low temperature stress condition(2-5℃),and MDA content and plasmalemma relative permeability increased during cold storage.which resulted in the occurrences of chilling injury of loquat fruits.however,The loquat fruits were treated with heat treatment and then stored in 2-5℃,The facts that respiration rate went up and stimulated the increment of synthesis of ethylene low temperature caused were alleviated obviously,moreover the increment of MDA content and lignin abnormal metabolism were repressed.cold-resist increase of cell membrane,and hence the degree of chilling injury was alleviated obviously.The pulp hardness increase and extractable juice rate decrease all had something to do with the cell wall material abnormal metabolism when the loquat fruits were stored at 2-5℃, moreover intimidation that low temperature caused could induce PAL activity rise quickly and abnormal increase of lignin synthesis,which also illuminated the occurrence of lignification during cold storage was a kind of maladjustment phenomenon of low temperature.It was thinked that SOD,POD and CAT were its enzyme defenseive system in plant adverse circumstances.During cold storage these enzymes of loquat fruits all had responsive hoist course,whcih was an adaptable reaction of loquat fruits to low temperature,howerver,their activities descended quickly.Although loquat fruits by way of heat treatment comparing its comparisons of non-heat treatment did exist the differences of reaction time and degree to low temperature adaptability,SOD,POD and CAT activities of loquat fruits by way of heat treatment enhanced and kept higher stability at last stages of all storage,which could alleviated chilling injury of loquat fruits.Learning from the cell morphologic observation ,we can see that the part subjected to invade was few layer pulp cells close to the coat of loquat fruits when stored at 2-5℃.The thin wall cell started to be flat even turn,and cytoplasm separated from cell wall further.Along with the extension of intimidation duringcoldstorage, The occurrences of chilling injury further caused epidermis organization to fall and increase of obvious water stains spot on the appearance of the loquat fruits.These series of courses also proved chilling injury and many other physiological changes were a kind of maladjustment phenomenon of loquat fruits during cold storage.This experiment result expressed that the technique of heat treatment to combine low temperature was an effective measure to keep loquat fruits fresh, and extend its life span.
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