乌蕨配子体发育及卵发生的显微观察

采用光学显微镜对乌蕨的配子体发育及卵发生的过程进行了研究,以阐明蕨类植物颈卵器发育特征,为揭示蕨类植物有性生殖机制以及鳞始蕨科的演化提供依据。结果表明:(1)乌蕨孢子黄褐色,具单裂缝,表面平滑或呈疣状纹饰;孢子接种12d萌发,萌发类型为书带蕨型,原叶体发育类型为铁线蕨型。(2)半薄切片观察表明,乌蕨颈卵器产生于原叶体生长点下方的表面细胞,即颈卵器原始细胞,该细胞经过两次分裂形成纵向3层细胞,最上层细胞发育为颈卵器的颈部壁细胞,中间层细胞即初生细胞再经过两次不等分裂产生颈沟细胞、腹沟细胞和卵细胞,此三细胞最初紧密贴合,随着颈卵器的发育,卵细胞与腹沟细胞间从两侧向中间产生分离腔,且腹沟细胞与颈沟细胞开始退化;分离腔逐渐向中间扩大,直至出现孔状结构,即受精孔;颈卵器发育后期,在卵细胞上表面形成染色较深的卵膜,颈沟细胞与腹沟细胞退化成絮状物。

Microstructural Observation on the Development of Gametophytes and Oogenesis in the Fern Stenoloma chusanum

The development of gametophytes and oogenesis in the fern Stenoloma chusanum were studied using microscopy technology.Results showed that:(1)The spores are brown,monolete,surface smooth or verrucous grain;spores germinate about 12 days after sowed.Spore germination type is Vittaria-type.Prothallus development type is Adiantum-type.(2)Section observations showed that the archegonium of the S.chusanum develops from a superficial cell called initial cell.The initial cell forms a tier of three cells by two divisions.The upper cell develops into an elongated neck.The middle cell,called primary cell,finally develops into a neck canal cell,a ventral cell and an egg by two unequal divisions.When new formed the periphery of the three cells is appressed closely to the jacket cells of the archegonium.During maturation,a separation cavity occurs between the egg and the ventral canal cell,from periphery to the middle.Then,the neck canal cell and the ventral canal cell began to degenerate.Separation cavity expanded toward the middle,until a pore structure,called fertilization pore,occurred.In the later stage of oogenesis,on the upper surface of the egg,an egg envelope forms,and the neck canal cell and the ventral cell degenerate into a mass of amorphous materials.This study elaborated in details the morphological characteristics of gametophytes and oogenesis in the fern S.chusanum,and has scientific significance in illustrating the archegonium development features and revealing the mechanism of sexual reproduction.