Study On The Membrane Stability Of Sweet Orange During Growth-Development And Storage

Citrus is one of the most important cultivating fruit in China. And the improvement of citrus quality is the most important task after entering of the WTO. AS the membrane is the important place of the cell physiologycal metablize of the fruit, keeping the integrality of the cell membrane is the most precondition of the citrus quality improvement.The material of the experiment was the middle-maturing 'Newhall' Navel orange, and late-maturing 'Washington Sanguine'. The process of the membrane peroxidation during the citrus product senescence was investegated in this study; the content of the experiment include that: free fatty acids which is the important component of the cell membrane, the superoxide anion which is an important factor causing membrane peroxidation, LOX, SOD, CAT enzyme which affecting the membrane integrality, MDA which is the product of the membrane peroxidation, the cell relative electrolyte leakage, proline which is the most important penetrative conditioner and some quality index of the fruit (flesh firmness, colour difference and s soluble solid content). The result showed that: the activity of LOX, SOD, CAT enzyme, the content of MDA, prodcution rate of the superoxide anion, and the cell relative electrolyte leakage changed gently during the growth-development. After riping, the acitivity of SOD, CAT enzyme reduced along with the senescence of fruit, but the activity of LOX increased. The content of MDA, the production rate of superoxide anion and the relative electrolyte leakage of the cell increased sharply along with the extend of the storage and the senescence of fruit, but the production of proline and the content of the free fatty acids decreased. The compare of two citrus cultivar showed that, the cell membrane of 'Nehall' Navel orange broke up more rapidly than 'Washington Sanguine'.The compare of the stability of the cell membrane of the 'Nehall' Navel oranges which were stored at low tempreture and on-tree showed that: the method of storage on-tree could effectively delay the reduction of the activity of SOD, CAT enzyme and the increase of the acitivity of LOX enzyme. It aslo delayed the increase of the prodcution rate of the superoxide anion, enhanced the flesh firmness. And the content of proline and free fatty acids in orange stored on-tree were more than the orange stored at low tempreture, but the relative electrolyte leakage is less. We can say that the method of storage on-tree could delay the senescence of 'Nehall' Navel orange effectively.The compare of the stability of the cell membrane of the 'Washington Sanguine' stored on-tree and at low temperature after the treatment of SA showed that the two methods all could delay the senescence of Washington Sanguine effectively.