The Relationship Between Sugar Metabolism And Respiratory Metabolism Throughout Fruit Development And Postharvest Of Korla Fragrant Pear(Pyrus Sinkiangensis Yu)

In this study,the responding relationship of sugar metabolism and respiratory metabolism throughout fruit development and postharvest of Korla fragrant pear(Pyrus sinkiangensis Yu),and the differences of sugar quality at climacteric and metabolic response of the fruits harvested at different maturity stages were analyzed by the measurements including metabolic enzyme activities,sugar contents,respiration rates of different respiratory pathways in attempt to assess the effect of metabolic interaction on sugar accumulation in fruit development and ripening,to explore the reaction of postharvest metabolic timing response with sugar contents,and to understand the effect of maturity stage on postharvest sensory quality and metabolic responding.The following are main results.1.During fruit development of 60-150 DPA(Days of post anthesis),either core or pulp,the metabolic interaction between sugar metabolism and respiratory metabolism differs in 2 patterns at 90 DPA before and after,and differs at 120 DPA of peel respectively.These metablic response in time order forms typical internal quality of of Korla fragrant pear by sugar accumulation composed principal component with fructose and glucose.2.Sucrose and sorbitol metabolisms in core were associated with respiratory metabolism of TCAC(Tricarboxyficacid cycle)and AP(Alternative pathway),in which the accumulation of major sugar component changed from starch to sucrose and to sorbitol in 60-80 DPA.The metabolism of starch,sucrose and sorbitol were clustered with the respiratory metabolism of PPP(Phosphopentose pathway),EMP(Embden-Meyerhof-Parnas)pathway and CP(Cytochrome pathway),as well as the major sugar component was converted from glucose to fructose to complete sugar accumulation,when core quality increased to 7.0g above in 90-150 DPA.3.The metabolism of starch,sucrose and sorbitol in pulp were clustered in which starch accumulated as the major sugar component in 60-80 DPA.Sucrose metabolism were clustered with the respiratory metabolism of EMP pathway,TCAC pathway,CP and AP,as well as the major sugar component was converted from sorbitol to sucrose,glucose,and fructose to complete sugar accumulation,when pulp quality increased to 50.0~100.0 g above in 90-150 DPA.4.The metabolism of starch and sorbitol in peel were clustered with the respiratory metabolism of PPP,EMP pathway and TCAC pathway,in which sorbitol and sucrose accumulated as the major sugar component in 60-120 DPA.Starch and sucrose metabolisms were clustered with the respiratory metabolism of TCAC pathway,CP and AP,as well as the major sugar component was converted from starch to glucose and fructose to complete sugar accumulation,when peel quality increased to 17.0 g above in 130-150 DPA.GPI(Glucose phosphate isomerase)and COX(Cytochrome oxidase)in three fruit parts were key enzymes of common crosslink in sugar metabolism and respiratory metabolism at the end of fruit development.5.Fruits of 3 maturity stages harvested at 130,140 and 150 DPA storaged at 5℃ had significant decrease of starch content with increases of soluble sugar contents in all fruit parts,and fructose was the highest content component and had the greatest contribution to all parts sweetness in postharvest.Fruit peel of 3maturity stages had the highest respiration rates in all fruit parts in storage,respiration rates including total respiration and different respiratory pathways,which were satisfied with curves fiting at peak completely.That suggested fruit postharvest climacteric was the accumulation effect of multiple pathways respiratory peaks from peel.6.In senescence deterioration of fruit postharvest,heating respiration has priority in respiratory metabolism of pulp and took organic acids as basic substrate,but glucose became the elementary substrate when the energy synthesis respiration made a leading.Substrates sourced from sucrose or sorbitol metabolizing involved in postharvest different stages of respiration metabolism of the riper fruit pulp,heating respiration and energy synthesis respiration of fruit harvested early became synchronized.Energy synthesis respiration had the priority in respiratory metabolism of core and peel,but would be alternated quickly to the heating respiration in riper fruit as well as elementary substrate altered from starch or sorbitol metabolite to sucrose metabolite.The fruit postharvest climacteric features were that,CP energy synthesis respiration jointed many hot spots of EMP and TCAC into metabolic centroid,after that altered to APheating respiration quickly with few metabolism hot spots linked.These metabolic processes of fruit peel took starch,sucrose,sorbitol and organic acids sourced elementary substrates,the alternation of energy synthesis respiration and heating respiration during postharvest climacteric delayed in riper fruit peel.7.The response of sugar metabolism and respiratory metabolism of all fruit parts post harvest was dispersing and depolymerizing in a downward trend,when the AOX played a key role during the metoblic responsing conversion in the end of electron transport.Fructose of all fruit parts had accumulated in highest throughout the fruit development,but reduced the content less than other components after harvest,since it is not a principal substrate for respiratory metabolism postharvest.Starch,sorbitol,glucose and sucrose are programming utilized in time order efficiently could maintain fruit sweetness and sugar quality of Korla fragrant pear.Fruit harvested at 140 DPA has better storability because postharvest respiratory peak of peel occured later,and sugar metabolism and respiratory metabolism of pulp response longer.