机械损伤对脐橙果皮组织结构的影响（英文）

Effect of Mechanical Damage on Organizational Structure of Postharvest Navel Orange Rind

由于机械损伤可以引起果皮油胞的破损和后续的油胞病症状,其被认为是脐橙果皮油胞病发生的主要原因;然而机械损伤也能促进其他果皮生理病害的发生。受机械损伤后,果皮的生理病害症状更加复杂,不能简单地归结于油胞病的发生。为了更好地阐明机械损伤后果皮生理病害的发生和发病进程,利用扫描电子显微镜和透射电子显微镜观察了机械损伤后‘奉节’脐橙果皮生理病害发生进程中的超微结构变化,同时测定果皮果胶、纤维素、木质素等结构物质含量和脂氧合酶活力、超氧阴离子自由基产生速率的变化。结果表明:机械损伤后,脐橙果皮细胞膜完整性受到破坏,黄皮层油胞细胞出现明显降解,进而导致油胞的破裂、橘油的释放以及白皮层和黄皮层的降解。机械损伤处理后,果实果皮脂氧合酶活力和超氧阴离子自由基产生速率在贮藏前期快速增加,果皮原果胶含量急剧下降,贮藏7~11 d,机械损伤果实果皮可溶性果胶含量显著高于对照组果皮(P<0.05)。本实验结果可为脐橙果皮受到机械损伤后超微观结构变化的原因提供参考。

Mechanical damage is the main reason for the occurrence of oleocellosis in citrus fruit because it can cause the rupture of rind oil glands and the consequent symptoms of oleocellosis. Nevertheless, mechanical damage also favors the development of other rind disorders. More complicated physiological disorder symptoms appear in the orange rind after mechanical damage, which cannot be simply attributed to the development of oleocellosis. To better elucidate the initiation and progression of mechanical damage-induced orange rind disorders, the ultrastructural changes occurring in ‘Fengjie’ navel oranges during these processes were investigated by transmission electron microscopy and scanning electron microscopy. The contents of pectin, cellulose and lignin, the rate of generation of superoxide anion radicals and lipoxygenase activity were also measured. Results indicated that after mechanical damage, the integrity of the cell membrane was lost and the cells of oil glands in the flavedo underwent an apparent degradation, resulting in the rupture of oil glands, and consequently the release of orange oil and the degradation of both the flavedo and albedo. During the early stage of storage after mechanical damage, the activity of lipoxygenase and the generation rate of superoxide anion increased steeply, and the content of protopectin reduced sharply. The contents of water-soluble pectin significantly increased from Day 7 to 11 relative to the control(P < 0.05). On the whole, the results from this study can provide some insights into the cause of the ultrastructural changes occurring in navel orange rind after mechanical damage.