灰枣和冬枣果实质地差异的解剖学观察及相关酶活性研究

Anatomical observation on the differences in the fruit texture between Huizao and Dongzao jujube and related enzyme activities

【目的】以果实质地差异明显的两个枣品种为试验材料,观察其发育过程中果肉细胞的显微结构,测定果实的含水量、硬度及细胞壁相关代谢酶的活性,并进行相关性分析,探究影响两种质地形成的关键因素。【方法】分别以灰枣(制干枣)和冬枣(鲜食枣)花后31(S1)、63(S2)、78(S3)、98(S4)和108 d(S5)的果实为试验材料,对果实发育过程中含水率、硬度,果肉细胞形态、细胞壁组分及代谢酶活性进行动态分析。【结果】(1)随着果实发育,灰枣和冬枣的含水率均呈先升高后下降的趋势,硬度均呈下降趋势,且灰枣硬度持续高于冬枣。(2)两个品种果肉细胞的变化均呈现先迅速增大后缓慢增大的趋势,但冬枣果肉薄壁细胞面积大于灰枣。(3)果肉细胞超显微结构观测显示,在S5时期,两个品种果肉细胞壁、中胶层已经明显降解,但冬枣相较灰枣其中胶层、内含物降解较慢。(4)两个品种总果胶以及纤维素含量整体呈逐渐降低趋势,且冬枣一直低于灰枣。(5)果实硬度与总果胶和纤维素含量呈显著正相关,与β-半乳糖苷酶(β-Gal)、α-L-阿拉伯呋喃糖苷酶(α-Af)、果胶裂解酶(PL)活性呈极显著负相关,多聚半乳糖醛酸酶(PG)活性与冬枣果实硬度、水分含量的相关性均极显著,但与灰枣相关性不显著。【结论】灰枣和冬枣质地品质的差异与细胞壁组分总果胶及纤维素含量、果肉细胞显微结构的差异相关,还与细胞壁代谢相关酶β-Gal、α-Af、PL有关,此外,PG在冬枣质地变化中也发挥关键作用。

【Objective】In this study,the microstructure of fruit pulp cells of two jujube(Zizyphus jujuba Mill.)varieties with obvious differences in fruit texture was observed,the water content,hardness and activity of cell-wall-related metabolic enzymes were measured,and correlation analysis was carried out to explore the key factors affecting the formation of the two types of textures.【Methods】The moisture content,hardness,pulp cell morphology,cell wall components and metabolic enzyme activities of dried jujube Z.jujuba‘Huizao’and fresh jujube Z.jujuba‘Dongzao’were used as test materials after 31 days(S1),63 days(S2),78 days(S3),98 days(S4)and 108 days(S5)after flowering.【Results】(1)As the fruit developed,the water content of both Huizao and Dongzao showed a trend of first increasing and then decreasing,hardness showed a trend of decreasing,and Huizao’s hardness was persistently higher than that of Dongzao.(2)The pulp cell changes of two varieties were presented first rapid increase and then slow increase trend,but Dongzao’s pulp parenchyma cell area was significantly larger than that of Huizao’s.(3)Fruit pulp cell ultrastructural observation showed that at the S5 period,the pectin layer of fruit pulp cell wall of the two varieties was obviously degraded,but the degradation of pectin layer and inclusions in Dongzao was slower compared to Huizao.(4)The total pectin and cellulose content of the two varieties as a whole showed a trend of gradual decrease,and Dongzao was always lower than the Huizao.(5)Fruit hardness was significantly and positively correlated with total pectin and cellulose content,and highly significantly and negatively correlated withβ-Gal,α-Af and PL enzyme activities,and the correlation between PG enzyme and Dongzao’s fruit hardness and water content was highly significant,but the correlation with Huizao was not significant.【Conclusion】The difference in texture quality between Huizao and Dongzao was related not only to the differences in total pectin and cellulose content of cell wall fractions and the microstructure of pulp cells,but also to the cell wall metabolism-related enzymesβ-Gal,α-Af and PL enzymes.Moreover,the PG enzyme played a key role in the Dongzao texture changes.