摘要
采用高压冷冻和低温替代技术对不同时期泌蜜前、泌蜜早期和泌蜜晚期的拟南齐(Arabidopsisthaliana L.)成熟花蜜腺的超微结构进行了研究。着重对小泡运输过程中是否与细胞质膜发生融合以及蜜腺组织中深色细胞与伴胞的区别等问题进行了讨论。拟南芥花中有一对较大的侧蜜腺以及2～4枚中蜜腺。中蜜腺位于2枚长雄蕊基部或它们之间,而侧蜜腺则位于两花瓣之间的短雄蕊附近。泌蜜前和泌蜜期,液泡的大小、高尔基体及内质网的数量、线粒体的分布以及质体内淀粉粒的大小都会发生一定的变化。当高尔基小泡从细胞内运输至细胞外时,并没有发生与细胞质膜融合的过程,与经典的“胞吐”假说不同。深色细胞在泌蜜期大量出现与筛分子旁的伴胞明显不同,前者与蜜腺顶端的气孔器相连,形成“通道”从而使蜜汁从蜜腺排出。
High pressure freezing and freeze substitution techniques were used to study the floral nectary of Arabidopsis thaliana L. focused on its ultiastructure of mature nectary at pre-secretory, early secretory and heavy secretory stages. Questions of whether or not the transported vesicles fuse with the plasmalemma, and whether or not the 'densely-stained cells' were comparable to companion cells during the secretory process were especially emphasized. The flowers of A. thaliana contained a pair of rather large lateral nectaries and 2 to 4 median ones. TTie median nectaries were situated at the bases of the two long stamens or between them while each of the lateral ones was situated nearby each short stamen and between two petals. Before and during the secretion changes in the size of vacuoles and starch grains in the chloroplasts, the number of dictyosomes and endoplasmic reticulum and the distribution of mitochondria occurred before and during the stage of secretion. It appears that transported vesicles from the dictyosomes were transferred directly from one nectariferous cell to another or to the exterior. They did not fuse with the plasmalemma when they left the cells. A great number of special 'densely-stained cells' were different from the companion cells nearby the sieve elements. It was suggested that a tunnel be formed by these 'densely-stained cells' connecting the stomata at the top of nectary leading the out-flow of nectar.
关键词
拟南芥
蜜腺
超微结构
高压冷冻
低温置换
Arabidopsis thaliana, Nectary, Ultrastructure, Vesicle secretion, High pressure freezing, Freeze substitution
