Studies On The Physiological And Biochemical Mechanism Of Xinjiang Apricot Fruit During The Period Of Developmental And Storage

Six Xinjiang apricot cultivars:early varieties (Baduyulvke and Kumaiti)、 medium varieties (Daguohuanna and Luntaixiaobaixi) and later medium varieties (Jianali and Hongdaike) were used as materials, physiological and biochemical characteristics changes in apricot fruit during maturation and postharvest stage were researched.These results provided the theoretical studies to the apricot fruits’ ripening and aging physiological mechanisms. The results showed as follows:1.Development period:early maturing varieties was52d,middle maturing varieties was70d,late-maturing varieties was77d.The development period showed "fast-slow-fast" growth trend, the second duration was longer. To maturity, fruit shape index reduced from1.2to1.1;the firmness fell to0.23～0.28kg/cm2, late-maturing varieties was slightly higher than that of early maturing varieties; Soluble solids、Vc protein and total sugar content were growth, late-maturing varieties>early maturing varieties; The total acid content decreased50%, late-maturing varieties was less than early ones.Apricot fruit’s fresh and dried ratio increased,dry matter content of late-maturing varieties was significantly higher than the early ones, significant differences (P<0.05).2. Apricot fruit has not breathing phenomenon during development period,membrane permeability increased, early maturing varieties was largest. Changes of SOD, POD and CAT activity was different, SOD is the most important, which had a sharp decline when cell membrane permeability had a sharp increased. SOD activity:late-maturing varieties> early maturing varieties.3. During fruit developmental, cell wall content decreased, soluble and ionic pectin content increased, to ripening period, baduyulvke contained the highest soluble pectin, was13.26mg/g; covalently bound pectin content increased first, to maturity showed downward trend; cellulose and hemicellulose showed downward trend, to ripening period, cellulose content decreased to1/3of the original; cellulase activity entirety rosed3times;pectinase activity:late-maturing varieties>medium maturing variety> early maturing varieties.4. Firmness with the content of the cell wall and pectin (soluble pectin and ionic pectin) showed a significant positive and negative correlation.5. The pulp cell volume is one of the main factors to determine the apricot fruit size. During development, pulp cell’s ultra-microscopic structure changes:fruit set period, the middle lamella has high electron density, showed bright-dark-bright structure, organelles complete, to mature, the mesoglea obvious degradation, chloroplast rupture, cell wall loose. Pulp cells cell walls in late-maturing varieties showed lower degradation of organelles, the mesoglea degradation rate was less than early maturing varieties,further to explain its storability better from the cell structure angle.6. Transcriptome of analysis for mature apricot fruit,the assembly results contigs sequence compared with Nr/Nt,could be inferred apricot fruits protein gene was higher similarity with peach fruit,mainly in ethylene synthesis process and softening related enzymes,similarity with Prunus armeniaca’s β-amylase、 protein kinase and lipoxygenase,similarity with complete mitochondrial genome of the Golden Delicious apple.Predicted similar to grape’s protein synthesis and metabolic processes related enzymes. pectinase of peach fruit and cellulase gene sequence of pear fruit downloaded from NCBI,similarity were97%and87%,pectinase play an important role in the apricot fruit ripening and softening.7. The postharvest apricot fruit had higher degree of softening, firmness can be used as an important indicator to measure quality of postharvest apricot fruit, late-maturing varieties higher than early ones, showed better storability. Flavor and nutrients (sugar, acid, Vc and protein)content consumptioned larger during storage time, quality declined, post-harvest preservation technology research should focus on how to better maintain the quality of apricot fruit during storage8. Apricot was respiratory fruit, the main reason about its not storability, during storage, respiratory peak time,membrane permeability increased rapidly and the content of harmful substances incriesed time consistent, protective enzymes variation with the variation of the content of harmful substances in line, Accumulation of harmful substances of late-maturing varieties is less than early maturing varieties, the cell membrane stability higher than the early ones, further illustrate its storability.9. During postharvest storage,pectinase and cellulase activity increased,to promote the degradation of pectin and cellulose.Cellulose,hemicellulose,and covalent binding content decreased, water-soluble and ionic pectin content were increased, Baduyulvke had the lowest content of cell wal,significant difference (p <0.05),It’s worth for exploring whether cell wall content as a storability evaluation index of apricot fruit.10. the rate of decline of the cellulose content and the increases of cell membrane permeability were the main factors which caused the decline of apricot fruits firmness during storage.11. The apricot fruit was not storability, mainly due to postharvest respiratory peak, after the peak appeared, the hardness and nutrient content decreased, cell membrane permeability increased, cell wall hydrolase activity increased, cell wall material degradation, The fruit quality rapid declined. The Storability of Late-maturing varieties were better than early varieties.