京白梨果实后熟软化过程中细胞壁代谢及其调控

 【目的】探讨细胞壁代谢与‘京白梨’果实软化的关系及其调控,为解决果实品质下降及迅速软化问题提供依据。【方法】用0℃、1-甲基环丙烯（1-MCP）和乙烯利处理‘京白梨’果实,测定细胞壁组分及其降解酶活性变化及调控效应。【结果】随着‘京白梨’果实后熟软化,果实细胞壁物质（CWM）、共价结合果胶（CSP）、半纤维素和纤维素含量减少,离子结合果胶（ISP）和水溶性果胶（WSP）含量增加;果胶甲酯酶（PME）和多聚半乳糖醛酸酶（PG）活性在采后3 d 后开始升高,分别在第9天和第12天出现活性高峰,α-L-阿拉伯呋喃糖苷酶（α-L-Af）和β-半乳糖苷酶（β-Gal）活性在采收时就开始升高,并持续到贮藏末期,但纤维素酶活性呈降低趋势。相关分析表明,果实硬度与半纤维素、ISP和CSP呈极显著相关,与WSP和纤维素呈显著相关;而β-Gal和α-L-Af不仅与硬度呈极显著相关,且与细胞壁组分的相关度均大于其它细胞壁降解酶,但纤维素酶未表现出相关性。0℃和1-MCP处理显著抑制了‘京白梨’果实纤维素、半纤维素与CSP含量的下降和ISP与WSP含量的增加,降低了α-L-Af、β-Gal、PME和PG活性,推迟果实软化;乙烯利的作用不大。【结论】采后‘京白梨’果实软化与细胞壁组分变化密切相关,细胞壁降解酶中,β-Gal和α-L-Af可能是果实早期软化的主要因子,PME和PG促进了果实后期软化,但纤维素酶作用不大。0℃和1-MCP能显著抑制‘京白梨’果实细胞壁代谢,延缓果实软化;乙烯利未显著促进果实软化进程。

Cell Wall Metabolism and Its Regulation in Harvested Pyrus ussuriensis Maxin.cv.Jingbaili Fruit During Ripening

【Objective】 This experiment was aimed to discuss the relationship between cell wall metabolism and fruit softening, and their regulation in harvested ‘Jingbaili’ pear to provide a theoretical basis for improving fruit quality and inhibiting fruit softening.【Method】 Fruits of pear cultivar ‘Jingbaili’ (Pyrus ussuriensis Maxin. cv. Jingbaili) were used to investigate the changes in cell wall compositions, their metabolism-related enzymes, and their regulation by low temperature (0℃) and ethylene (1-MCP or ethephon). 【Result】 The contents of cell wall materials (CWM), covalent pectin (CSP), cellulose and semicellulose decreased, while the content of ionic pectin (ISP) and soluble pectin (WSP) increased during fruit softening. Activities of pectinesterase (PME) and polygalacturonase (PG) enhanced on the 3 rd day after harvest, and their peaks appeared on the 9th and 12 th days, respectively. Activities of β-galactosidase (β-Gal) and α-L-arabinofuranosidase (α-L-Af) increased initially and maintained this trend by the end of storage, while cellulase activity declined during fruit softening. Analysis of correlation showed that semicellulose, ISP and CSP had more relationship with firmness than WSP and cellulose; β-Gal and α-L-Af had more significantly correlation not only with firmness, but also with cell wall compositions than the other enzymes. Treatments with 0℃ and 1-MCP decreased the declines in cellulose, semicellulose and CSP contents, as well as the increases in ISP and WSP contents. Meanwhile, activities of β-Gal, α-L-Af, PME and PG were inhibited significantly, postponing fruit softening, but fruit softening was not facilitated by ethephon. 【Conclusion】 The changes in cell wall compositions had an important relationship to fruit ripening, which were resulted by their metabolism-related enzymes. Among them, β-Gal and α-L-Af could play more roles at early softening stage, PME and PG accelerated late fruit softening, while cellulase showed little effect. Fruit softening was obviously inhibited by 0℃ or 1-MCP, but it was not markedly facilitated by ethephon.