高氧气调包装对绿芦笋木质化的调控机制研究

Green asparagus is very popular with consumers for its appealing flavor, high vitamins, minerals and other bioactive compounds. It is a vegetable with very high nutritive and functional value. The harvest period of green asparagus is relatively concentrated. After harvest, the vegetable rapidly senesces and loses its commodity due to its high respiration rate. It has 2-3 days shelf life under ambient temperature. Lignification is the main factor of restricting green asparagus storage time. It is a key and urgent problem how to prevent green asparagus lignifying during storage time. Our previous research confirmed that high oxygen atmosphere packaging effectively delayed the lignification in postharvest green asparagus. However, the mechanism involved remains to be further investigated. The project will explore the biosynthetic pathway of lignin in postharvest green asparagus. Based on investigations from the phenylpropnaoid pathway, the proposal will study the changes of structure and composition of cell wall and the distribution of lignin in postharvest green asparagus during lignification, clarify the internal relationship of phenolic compounds, which are precursors of lignin synthesis, reactive oxygen species and lignin deposition, understand the molecular basis of key enzymes of lignin biosynthesis, and reveal the regulation mechanism of high oxygen atmosphere packaging on delaying the lignification of postharvest green asparagus. The results from the research will provide theoretical basis for regulation of lignification of postharvest fruits and vegetables.

绿芦笋嫩茎味美鲜嫩，富含维生素、矿物质、氨基酸及其它功效成分，是一种营养、保健价值极高的蔬菜，深受消费者的喜爱。但绿芦笋采收期相对集中，采后呼吸旺盛，常温下2～3d即失去商品性。木质化衰老是限制绿芦笋贮藏寿命的主要因素，如何防止绿芦笋的木质化败坏，是绿芦笋贮藏中迫切需要解决的关键问题。我们前期研究证实，高氧气调包装可延缓采后绿芦笋的木质化进程，但其机制尚不明确。本项目以采后绿芦笋的木质素生物合成途径为核心研究内容，从苯丙烷类代谢途径入手，研究高氧气调包装条件下采后绿芦笋木质化过程中细胞壁结构成分的变化、木质素在亚细胞结构中的定位分布规律，木质素合成前体物质酚类化合物、活性氧代谢与木质素积累之间的内在联系，并进一步从木质素合成关键酶基因表达水平上探讨高氧气调包装对采后绿芦笋木质化的调控机制，揭示高氧气调包装延缓采后绿芦笋木质化进程的作用机制，为采后果蔬的木质化调控提供理论基础。

不同品种、不同采收期绿芦笋的品质存在很大差别，主成分分析结果表明，“格兰德”绿芦笋的综合品质最佳，春季采收的绿芦笋的品质优于夏季。高氧气调包装（60%O2+20%CO2+20%N2，80%O2+20%CO2，100%O2）格兰德绿芦笋的质构、细胞壁结构成分的变化存在明显差异，60% O2、80% O2高氧气调包装绿芦笋的剪切力较小，嫩度较好，其细胞壁结构中的木质素、纤维素、半纤维素以及总果胶含量的上升较100% O2包装实验组和空气包装对照组缓慢，这表明60% O2、80% O2高氧气调包装可有效延缓绿芦笋韧性的增加及细胞壁结构成分的变化。木质素合成前体物质酚类化合物阿魏酸和咖啡酸不受高氧气调包装条件的影响，但香豆酸含量的上升能够被高氧气调包装有效抑制。采用荧光显微镜、植物学染色及透射电子显微镜，观察绿芦笋细胞壁中木质素的沉积和分布规律，结果发现60% O2、和80% O2高氧气调包装绿芦笋细胞壁中胞间层和角隅部分的木质素沉积和增厚现象较轻，S型木质素和G型木质素的比例（S/G）升高缓慢，这表明60% O2和80% O2高氧气调包装可以有效延缓绿芦笋的木质化进程。高氧气调包装能够激活活性氧清除酶，减少ROS的积累，保护绿芦笋的抗氧化系统，延缓绿芦笋的木质化衰老，且其效果强弱顺序依次为60% O2、80% O2、100% O2。高氧气调包装绿芦笋的PAL、POD、CAD基因表达水平相对较空气包装组低，这说明高氧气调包装可能直接或间接影响着木质素合成关键酶基因的表达，从而有效延缓绿芦笋的木质化进程。以上结果表明，高氧气调包装通过调控木质素合成关键酶基因的表达，延缓绿芦笋细胞壁中木质素的沉积，从而有效延缓绿芦笋的木质化进程，且60% O2和80% O2高氧气调包装最为有效。