Effects Of Harvest Maturity On Storage Quality Of Nectarine And The Flesh Cell Ultrastructural

The fruits of the nectarines variety 'Qinguang 2' were used to study the effects of five harvest maturities on storage quality and the ultrastructural change in the flesh cells during cold storage. The main results were as follows:1. With the maturity nectarines increased, the hardness, titratable acid content declined, and fruit weight, soluble solids content declined.2. During cold storage, the respiration peak of fruit at maturity gradeⅣreached latestly. Fruit at maturity gradesⅠ,ⅡandⅤreached their ethylene peak latestly on the 15th day after their storage,and fruit at maturity gradesⅢ,Ⅳwere on the 20th day, and the ethylene peak ofⅢwas higher thanⅣ. Ethylene peak presented earlierly than respiration peak 5～10d in every maturity fruit, and the order time was consistent.3. During cold storage,the less mature the fruits were higher PPO, POD activtity and their peak presented earlierly. During late storage, the less mature the fruits were higher MDA content and SOD activity.4. The symptom chilling injury of the nectarines variety 'Qinguang2'was unconspicuous, but after cold storage in room temperature, the respiration rate increased, the symptom which fruits were not normal soiling presented. Chilling injury of the less mature the fruits were more serious.5. Fruits at maturity gradeⅠ,Ⅴwere hardly worth to storage. At maturity gradeⅣ(the fruit appeared ivory and had the SSC of 11.4%, the hardness of 7.3 kg.cm^-2) had highr hardness, SSC, ratio of good fruits, and best storage effect. Fruits used storage must be harvested in a propriety earlier date.6. In the harvest day, the ultrastructural of mesocarp cells of nectarine maturity gradeⅠ,ⅡandⅢlined up in order concentrated, large vacuolated cells. The cytoplasm was spread along the periphery of the cell, against the cell wall. The cytoplasm was,rich in organelles: plastids, mitochondria, etc. Cell wall structure was in integrity between cell wall and middle colloidial layer structure was high density of electron and Shape-Shading-Shape structural. The structure of chloroplast was integrity, osmiophilic granule was dispersing in plastids. The ultrastructural of mesocarp cells of fruits maturity gradeⅣwas slightly different to maturity gradeⅠ,ⅡandⅢ. The cytoplasm becomes deformable and cell wall degenerated adherent cells separated. Fruits at maturity gradeⅤhad been completely mature, middle collodial layer dissolved, density of electron decreased, gap junctional intercellular increased, microfibril loosed. The plasmolysis generally appeared in the cells, tonoplast membrane breakeage.7. Mesocarp cells of nectarine appeared completely the senescence characteristic after storage 50d. Structural cell were irregular, polymerization between cells lost, gap junctional intercellular enlarged. Cell wall was crinkle bend, middle collodial layer dissolved, primary wall drifted, floc on the cell wall increased.Structural cell wall of fruit at maturity gradeⅣandⅤwere partly collapsed and resulted in fruits softening.Every maturity grade appeared the plasmolysis and tonoplast membrane breakeage. Contents ofcell organelle, vacuole and protoplasm dissolved with each other. Cell regionalization system was seriously damaged. Cell organelle degraded or deformed, cell contents decrease, empty cavity cell, physiological metabolic disorder.