【摘要】 该研究应用透射电镜技术,对生长发育过程中的文冠果果实的韧皮部及其周围薄壁细胞的超微结构进行了观察,以探讨文冠果果实同化物韧皮部卸载的细胞学路径及其机理。结果显示:(1)文冠果果实发育过程中,筛分子细胞胞腔较空,几乎没有细胞器,但有类似于囊泡的丝状不定型物存在;伴胞胞质浓密且细胞器丰富,液泡化程度不一,大多数存在多个小液泡;薄壁细胞具有中央大液泡,发育中期富含线粒体、高尔基体、内质网等细胞器,并存在囊泡运输现象,发育后期细胞器发生降解,说明随着果实生长发育,果实内物质代谢和转运活跃程度逐渐下降。(2)果实发育过程中筛分子和伴胞之间始终有胞间连丝,薄壁细胞之间也一直存在大量的胞间连丝,而筛分子-伴胞复合体与薄壁细胞之间只有在果实发育前期和后期存在一定数量的胞间连丝,发育中期却几乎没有胞间连丝。研究结果表明,文冠果果实发育过程中同化物韧皮部卸载路径可能发生了共质体途径-质外体途径-共质体途径的转变。更多还原

【Abstract】 In this study, we systematically investigated the ultrastructure of the phloem and surrounding parenchyma cells using transmission electron microscopy during the development process of Xanthoceras sorbifolium Bunge fruit, to understand the unloading pathway and mechanism during the fruit development. The results showed:(1) during the fruit development process, the cell cavity of the sieve element(SE)was empty and few organelles exited, but there were some vesicle-like and microfibril-like structures in SE. With increase of cytoplasm density and organelles abundance, the degree of vacuolization in companion cell(CC)varied, and most of them had multiple small vacuoles; Phloem parenchyma cell(PP)had large central vacuoles, and vesicle transport occurred in the middle stage of development. They were rich in organelles such as mitochondria, golgi bodies and endoplasmic reticulum, which degraded at the later stage of development. This indicated that the metabolism and substances transport in fruit decreased gradually with the fruit development.(2) During the development of fruit, there were always some plasmodesmata between SE and CC, and lots of plasmodesmata between CC. However, only a certain number of plasmodesmata existed between the SE-CC complex and PP at the early and late stage of fruit development, but almost no plasmodesmata existed at the middle stage of fruit development. Based on the above results, we concluded that the unloading pathway of assimilate changed from symplastic to apoplastic and then to symplastic during the fruit development.更多还原