| “Xiaobai” apricot is one of the main cultivars in xinjiang. “Xiaobai” apricot has a short harvest period and short storage life. The shelf life is usually only 3-5 days. However, because of apricot is climacteric fruit, flavor compounds loss quickly in low temperature storage process. The phenomenon shows that effects of the value of edible and commodity in apricot fruit. Nitric oxide(NO) has emerged as an important signal molecule with diverse physiological functions in plants.NO has been demonstrated to delay the process of deterioration. The effects of NO fumigation on characteristics of harvested “Xiaobai” apricot during at low temperature storage were investigated.The optimum concentration of NO and treatment period were obtained. The contents of organic acids were measured by HPLC in “Xiaobai” apricot fruit. The change of contents of organic acids and the expression of organic acid metabolism related genes were studied. The regulatory mechanism of NO treatment on organic acid metabolism was also explored in postharvest apricot fruit.The main results are as follows:1. The optimum concentration of NO was 110 μL/L and treatment period was mature green stage for “Xiaobai” apricot fruit. NO treatment significantly delayed the decrease of firmness,delayed color development and kept the good external appearance. In addition, NO treatment could reduce the membrane lipid peroxidation and maintain the integrity of the cell membrane. It also increasing the capacity for free radical scavenging. So NO treatment could delay the metabolic disorders caused by senescence, and extend the shelf life of “Xiaobai” apricot fruit.2. HPLC was applied to determine organic acids in “Xiaobai” apricot fruit. The chromatographic column was performed on a Platisil ODS-C18 column at 30 ℃, the mobile phase was CH3OH-0.01 mol/L KH2PO4(v/v, 3:97), p H=2.4, the detection wavelength was 210 nm, the sample volume was 10 μL at a flow rate of 0.4 m L/min.3. The main organic acid components were malic acid and citric acid in “Xiaobai” apricot fruit. 110 μL/L NO treatment showed an increased level of malic acid and citric acid, and reduced the rate of organic acid metabolism by analysing control and 110 μL/L NO treatment on the organic acid metabolism.4. Effects of NO treatment on the activity of organic acid metabolism enzymes on apricot fruit at mature green stage. The results show that the metabolic enzymes were ME(Malic enzyme), MDH(Malate dehydrogenase), CS(Citratesynthase), PEPC(Phosphoneolpyur-vatecarboxylase), IDH(Isoeitartedehydorgenase) and Cyt-ACO(Cytoplasmic Aconitase) respect-ively. MDH is an important enzyme of malic acid synthesis. ME is the key enzyme of malic acid degradation. CS and PEPC enzymes are associated with citric acid synthesis. IDH and Cyt-A-CO enzymes are associated with citric acid degradation. 110 μL/L NO trea-tment can improve CS, PEPC and MDH activity, but decrease IDH and Cyt-ACO activity.NO treatment improved the contents of malic acid and citric acid, and delayed the loss of organic acid on postharvest “Xiaobai” apricot fruit.5. RT-PCR method was used to clone Pa MDH, Pa ME, Pa CS, Pa PEPC, Pa ACO and Pa IDH genes. The length of genes were 243 bp, 257 bp, 349 bp, 182 bp, 212 bp, 100 bp respectively,which were purpose fragments by BLAST.6. Effects of NO treatment on the expression of organic acid metabolism related genes in apricot fruit at mature green stage. The results show that 110 μL/L NO treatment improved the expression of Pa MDH gene, and decreased the expression of Pa ME gene. Meanwhile, 110 μL/L NO treatment delayed the expression peak of Pa CS, Pa PEPC and Pa IDH genes, so maintained the contents of malic acid and citric acid. However, the content of citric acid declined due to 110μL/L NO treatment improved the expression of Pa ACO gene during the ripening process. |
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