| The kiwifruit was ethylene-sensitive fruit,so it was easy to become soft and decomposed at room temperature.Storing at low temperature was beneficial to alleviating the process of ripening and senescence,and extending the storage time.However,the kiwifruit was sensitive to low temperature and easily to metabolic disorders and cell damage.One of the main physiological functions of melatonin(MT)in living organisms is anti-aging and anti-stress effects.However,the research of the effects of exogenous melatonin treatment on the quality maintenance and cold resistance of horticultural products were rarely reported.This study with the 'Huayou' kiwifruit as material,studied the effect of different concentration of melatonin treatment on postharvest fruit chilling injury and senescence in fruit,selected effective concentration,and then analyzed the function of melatonin from physiological and the expression level of related gene transcription,in order to provide a scientific basis for exploring an effective way to regulate the chilling injury and senescence in kiwifruit.Postharvest kiwifruits(Actinidia Chinensis)were grouped dipped in 0,0.05,0.1,0.2,0.5 m M melatonin(MT)solution for 10 min at room temperature,then stored at 0±0.5?(90%~95%RH)for 90 d.The results showed that:1.With the increase of the storage time,the hardness and chromaticity of the fruit were gradually decreased,and the weight loss rate and the decay rate gradually increased.The0.05,0.1,0.2 m M MT treatment had the effect of delaying the decline of kiwifruit firmness and chromaticity,keeping lower of the weight loss rate and rotting rate after the storage,and0.1 m M MT had the most.2.Compared with that in control,0.1 m M MT effectively reduced the respiration rate and ethylene production,delayed the appearance of ethylene peak,and reduced the activity of amylase,increased ascorbate peroxidase(APX)activity and glutathione reductase(GR)activity,significantly increased the contents of ascorbic acid(As A)and glutathione(GSH),delayed the decline of the starch contents.3.With the extension of cold storage,the chilling injury of kiwifruit aggravated gradually,the chilling injury rate and the chilling injury index were gradually increased,0.1m M MT delayed the chilling injury occured time of fruit effectively,and reduce the chilling injury rate and chilling injury index significantly.4.0.1 m M MT maintained higher superoxide dismutase(SOD),catalase(CAT),and reduced the accumulation of O2-and H2O2,thereby reducing the damage to the cell membrane by low temperature and delaying the increase of relative electrolytic leakage and MDA content.5.The lignified cells are closely arranged in the near to epidermal tissue and the cells are smaller,on the contrary,closed to the core,the cells are larger and looser;Lignin is mainly concentrated inside the cell wall.0.1 m M MT treatment reduced the lignified cell of the fruit significantly.And at the storage,MT treatment inhibited the increase of lignin content in kiwifruit effectively.6.At the early of the storage,PAL enzyme activity of kiwifruit with MT treatment was significantly lower than control,MT delayed the peak time of CAD activity of fruit,and reduced the enzyme activity peak,inhibited the increase of lignin content.The activity of4-CL of fruit with 0.1 m M MT,were significantly lower than control,during the whole storage except the storage 20 d and 40 d,and MT reduced the the relative expression of Ac4CL1,Ac4CL2,similar to lignin content,thus Ac4CL1,Ac4CL2 can respond to exogenous melatonin treatment,related to the inhibition of lignin content increased of kiwifruit.To sum up,pre-storage application of 0.1 m M MT can alleviated the process of ripening,senescence and chilling injury of 'Huayou' kiwifruit under low temperature storage conditions. |
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