发菜的显微及亚显微结构的观察

通过光学显微镜、扫描电镜和透射电镜的观察、了解到一条发菜原植体大约由数十万计的念珠状细胞所组成,其藻丝多为单链,但也发现有分枝现象。整个原植体包被着厚薄不均的胶质鞘,外观粗糙,沟稜状起伏,且多裂隙。念珠状细胞为典型的原核细胞。细胞壁有三层结构,中央为色浅的核质区,四周为细胞质区其中散布着大量膜层薄而散乱的类囊体,膜上附有大量 rRNA 和藻胆体颗粒。还发现有膜层密集形如指纹的小类囊体。在细胞质中还分布着结构颗粒,多角体、聚磷酸体等嗜锇物质结构.一般细胞都具有分裂能力,方式多为横缢,先是细胞壁逐渐向中央扩展,最后将母细胞分成两个子细胞.从异形胞的结构特征来看,主要功能是渡过恶劣环境以保存物种。

OBSERVATIONS ON MICROSCOPIC STRUCTURE AND ULTRASTRUCTURE OF NOSTOC FLAGELLIFORME

Using the light microscope,scanning and transmission electron micros- copes,it is found that each individual Nostoc flagelliforme is composed of hundreds and thousands torulose cells.The filaments are uni-tr.ichome with branches in some cases.The thallus is surrounded by a mucoid sheath with different thicknesses,rough surface,and numerous craeky appearance.The Nostoc flagelliforme cells are typical prokaryote cells in which there is no discrete nuclear body.However,nucleoplasm exists, occupying the center of the cells.The cell wall of this prokaryote cell is three-layer- ed.Between the nueleoplasm and the wall,a great quantity of thylakoids disperse.Mo- reover,structured granules,polyhedral and polyphosphate bodies intersperse.All of vegetative cells seem to be able to divide.The reproductive manner is of horizontal split,i.e.the regenerated new cell walls expand from periphery towards the center, then the mother cells constrict and finally split into two daughter cells.In our opinion, the function of this structural characteristic of heterocysts is to endure extreme envi- ronment,so that they are able to maintain their species progeny.