南丰蜜橘果实纤维素代谢与化渣的关系研究

以化渣性好的‘沙糖橘’为对照，研究南丰蜜橘（‘南丰蜜橘97-1’和‘南丰蜜橘97-2’）果实发育过程中囊衣和汁胞的纤维素含量及相关代谢酶活性与化渣性的关系。研究结果表明，成熟期两个南丰蜜橘品种囊衣纤维质构指标（纤维强度、纤维延展性和纤维韧性）均显著高于‘沙糖橘’，‘南丰蜜橘97-1’显著高于‘南丰蜜橘97-2’；化渣性由好至劣感官评价结果为‘沙糖橘’>‘南丰蜜橘97-2’>‘南丰蜜橘97-1’。囊衣细胞壁的超微结构显示，果实成熟期囊衣细胞壁纤维素微纤丝分布密度由高到低为‘南丰蜜橘97-1’>‘南丰蜜橘97-2’>‘沙糖橘’。两个南丰蜜橘品种和‘沙糖橘’囊衣及汁胞的纤维素含量在整个果实发育过程中均呈下降趋势，以果实膨大前期至中期下降较快。除果实膨大前期外，‘南丰蜜橘97-1’囊衣的纤维素含量均显著高于‘沙糖橘’。与囊衣相比，汁胞中纤维素含量较少，并且在相同果实发育期两个南丰蜜橘品种往往低于‘沙糖橘’。酶活性分析表明，内切葡聚糖酶（Cx）、外切葡聚糖酶（C1）和β–葡萄糖苷酶的活性在果实膨大中期迅速升高，并且南丰蜜橘囊衣中的活性均高于‘沙糖橘’。囊衣中Cx和β–葡萄糖苷酶与囊衣纤维素含量极显著负相关，C1与囊衣纤维素含量显著负相关。结论：南丰蜜橘果实化渣性与囊衣纤维素密切相关；果实膨大前期至中期是纤维素降解的重要时期，Cx酶和β–葡萄糖苷酶是影响该过程的关键酶。

Studies on the Relationship Between Cellulose Metabolism and Fruit Mastication Trait of Nanfeng Tangerine

‘Nanfeng tangerine 97-1’and‘Nanfeng tangerine 97-2’were used as materials，and ‘Shatangju’with superior mastication was selected as control. The cellulose contents and the activities of exoglucanase（Cl），endoglucanase（Cx）and β-glucosidase that related to cellulose metabolism were measured in the fruit segment membrance and juice sac during the fruit development. The results showed that the segment membrance fiber strength，ductility and tenacity were significantly higher in‘Nanfeng tangerine 97-1’than those in‘Nanfeng tangerine 97-2’，and those in‘Nanfeng tangerine 97-2’were significantly higher than in‘Shatangju’. Sensory evaluation indicated that the mastication trait of ‘Shatangju’，‘Nanfeng tangerine 97-2’and‘Nanfeng tangerine 97-1’was superior，moderate and inferior，respectively. The cell wall ultrastructure of segment membrane displayed that the distribution density of cellulose microfibrils was the highest in‘Nanfeng tangerine 97-1’，followed by‘Nanfeng tangerine 97-2’and‘Shatangju’. The cellulose contents in the three cutivars showed a decline trend during the fruit development. It declined rapidly from the early stage to the medium stage of fruit cell expansion. The cellulose content in‘Nanfeng tangerine 97-1’segment membrance was significantly higher than that in ‘Shatangju’during the fruit development excerpt for early expanding stage. Compared to segment membrance，juice sac had lower cellulose content. Moreover，the cellulose content in‘Nanfeng’tangerine juice sac was lower than that in‘Shatangju’. In addition，the activitives of Cx，C1 and β-glucosidase increased rapidly in the medium-term of fruit cell expanding stage，and were generally higher in‘Nanfeng’tangerine than those in‘Shatangju’at the same fruit development stage. In segment membrance，significant negative correlation was generally or significantly found between Cl and cellulose content，β-glucosidase and cellulose content，and Cx and cellulose content，respectively. In conclusion，the mastication of ‘Nangfeng’tangerine is possibly related to cellulose in segment membrance. Moreover，the critical period of cellulose degradation is from the early stage to the medium stage of fruit cell expansion when the Cx and β-glucosidase play key roles in the process.