The Regulation Mechanism Of P-coumaric Acid Treatment Alleviates Chilling Injury In Postharvest Peach Fruit

In this paper,‘Shahong' peach fruit were treated with 0.5 m M p-coumaric acid(p-CA)and then stored at 4°C for 28 days to study effect of p-CA on chilling injury(CI)physiology and the regulation mechanism that included soluble sugars,phenolic compounds,polyamines,nitric oxide(NO)and ?-aminobutyric acid(GABA)metabolisms.1.Effect of 0.5 m M p-CA on CI physiology during low temperature storage was studied.The results showed that 0.5 m M p-CA treatment effectively delayed the development of CI in peach fruit,as which was illustrated by p-CA treated fruit showing lower CI index,respiration rate,weight and firmness losses,and increases in the contents of soluble solid and malondialdehyde than control fruit.2.Effect of 0.5 m M p-CA on soluble sugars metabolism in peach fruit during low temperature storage was studied.The results showed that p-CA treatment significantly enhanced the activities of sucrose phosphate synthase(SPS),sucrose synthase synthesis(SS-synthesis),hexokinase(HK)and fructokinase(FK),but inhibited the activities of sucrose synthase cleavage(SS-cleavage),acid invertase(AI)and neutral invertase(NI),which resulted in the higher sucrose and sorbitol contents,but the lower glucose and fructose contents that might contribute to promoting the chilling tolerance of peach fruit.3.Effect of 0.5 m M p-CA on phenolic compounds metabolism and antioxidant capacity in peach fruit during low temperature storage were studied.The results showed that p-CA treatment stimulated the activities of shikimate dehydrogenase(SKDH),phenylalanine ammonia lyase(PAL),cinnamate-4-hydroxylase(C4H)and 4-coumarate coenzyme A ligase(4CL),but inhibited polyphenol oxidase(PPO)and peroxidase(POD)activities,which contributed to the higher accumulation of total phenolic in peach fruit,and thus enhanced DPPH,hydroxyl radical and superoxide anion radical scavenging capacity.This study indicated that the alleviating effect of p-CA on CI was associated with its ability to regulate phenolic compounds metabolism and antioxidant capacity in peach fruit.4.Effect of 0.5 m M p-CA on the metabolisms of polyamines,nitric oxide and ?-aminobutyric acid in peach fruit during low temperature storage were studied.The results showed that p-CA treatment stimulated the activities of arginine decarboxylase(ADC)and ornithine decarboxylase(ODC),and thus led to putrescine(Put),spermidine(Spd)and spermine(Spm)accumulation in peach fruit.p-CA treatment elevated NO content by increasing nitric oxide synthase(NOS)activity.The treatment also significantly enhanced the accumulation of GABA content associated with increase in the activities of glutamate decarboxylase(GAD),diamine oxidase(DAO)and polyamine oxidase(PAO),but decrease in ?-aminobutyric acid transaminase(GABA-T)activity.Such synergistic production of these three compounds was conductive to protecting p-CA treated peach fruit from chilling stress.