宁夏枸杞果实韧皮部及其周围细胞超微结构研究

Ultrastructure of Phloem and the Flesh Sink-cells during Fruit Development of Lycium barbarum

应用透射电镜技术研究了宁夏枸杞果实韧皮部细胞的超微结构变化。结果表明:(1)随着枸杞果实的发育成熟,果实维管组织中的韧皮部筛分子筛域逐渐变宽,筛孔大而多,通过筛孔的物质运输十分活跃;筛分子和伴胞间有胞间连丝联系,伴胞属传递细胞类型,与其相邻韧皮薄壁细胞和果肉薄壁细胞连接处的细胞界面发生质膜内突,整个筛分子/伴胞复合体与韧皮薄壁细胞之间形成共质体隔离,韧皮部糖分的卸载方式主要以质外体途径进行。(2)韧皮薄壁细胞间的胞间连丝较多,而韧皮薄壁细胞与果肉薄壁细胞的胞间连丝相对较少,但果肉薄壁细胞间几乎无胞间连丝;果肉薄壁细胞之间胞间隙较大,细胞壁和质膜内突间形成较大的质外体空间,为质外体的糖分运输创造了条件。(3)筛管、伴胞、韧皮薄壁细胞和果肉薄壁细胞中丰富的囊泡以及活跃的囊泡运输现象,暗示囊泡也参与了果实糖分的运输过程。研究推测,枸杞果实韧皮部同化物的卸载方式以及卸载后的同化物运输主要以质外体途径为主。

On the base of the structural development of pericarp of Lycium barbarum L. , the ultrastructure of phloem and the flesh sink-cells during fruit development was studied by the electron microscope technol- ogy. The results showed： （1）with the fruit growing,the sieve plate with large and much sieve pores,where active substance transport was observed in SE. Most, if not all, of the CC were transfer cells. Numerous plasmodesmata were observed between SE and CC （SE/CC） ,but there were almost no plasmodesmata be- tween the SE/CC complexes and phloem parenchyma cell. Plasma membrane invagination was observed in adjacent between companion cell and phloem parenchyma cells. There was a symplasmically isolated be- tween the SE/CC complex and its surrounding cells over the fruit development,which was available to sug- ar phloem unloading by apoplast pathway. （2）Numerous plasmodesmata were also observed between the phloem parenchyma cells,on the contrary,there were almost no plasmodesmata between phloem parenchy- ma cell and fruit parenchyma cell and even between fruit parenchyma cells. （3）The larger intercellular space among the fruit parenchyma cells and apoplast space caused by cell wall and plasma membrane invag- ination,which were in favour of sugar post-phloem transporting by apoplastic pathway. Vesicles were ob- served to participate in assimilates unloading and transporting. Based on the above results, we concluded that it was an apoplast way that existed in phloem unloading and after unloading of photosynthate trans- portation in fruit of Lycium barbarum L..