Effects And Physiological Mechanism Of Exogenous Quercetin On Fruit Senescence In Apples

Flavonoids are a group of polyphenolic compounds diverse in chemical structure and characteristics. They have a wide of biological effects, including antioxidation, free radical scavenger and chelators of divalent cations etc. And quercetin, the more stronger scavenger of 1O2 can inhibit the damage of carotenoids caused by 1O2 effectively. The ability of scavenging oxygen radical, antioxidation is higher.Two cultivars of apple, "Starkrimson" and "Jonagold" were used as materials to examine the regulating effects of quercetin on cell membrane system, ethylene biosynthesis and the activity of SOD,POD,IOD. The main results were as follows:1. The exogenous quercetin played an important role in protecting cell membrane. The exogenous quercetin could inhibit the LOX activity of "Starkrimson" in vitro effectively. After the treatment of 0.2mmol/L on, the activity of LOX was lower than the control's in 20 days.After spraying on "Starkrimson" at August 1st, August 21st and September 1st, quercetin could inhibit lipid peroxidtion of the fruit discs of. After the treament of 0.02,0.2 and 2mmol/L quercetin on fruit discs in Shours, the contents MDA was lower than the control's.The treaments of quercetin with 0.02,0.2 and 2mmol/L of the "Starkrimson" flesh discs decrease the conductivity after culturing 12 and 24 hours.The treaments of quercetin with 0.2 and 2mmol/L of the flesh discs of "Starkrimson" and decreased O-2 after 6 hours.The above results indicated that quercetin was able to dely the senscence of fruit though protecting the membrane system.2. The treatment of quercetin with 0.02, 0.2mmol/L could increased the POD actibity of "Starkrimson" flesh discs. But the POD activity of "Jonagold" flesh discs among these treatment hadn't significant difference.The treatment of 0.2 mmol/L quercetin on "Starkrimson" in vitro, the results indicated that it could increased the POD activity at the early period. 0.2 and 2 mmol/L quercetin increased the SOD activity at the later period.3. The culture of fruit discs indicated that the treatment of quercetin with 0.02, 0.2 and 2mmol/L could inhibit IOD activity of "Jonagold" discs, and the percentage of inhibition of 0.2mmol/L was the highest. 0.2mmol/L quercetin inbition the IOD activity of the "Starkrimson" discs. The other treatments were not significant difference.4. The culture of fruit discs indicats that the treatment of quercetin with 0.02, 0.2 and 2mmol/L inhibited ethylene biosynthesis.