扇叶铁线蕨配子体发育及卵发生的显微观察

Microstructural Observation on the Development of Gametophytes and Oogenesis in the Fern Adiantum flabellulatum L.

采用显微观察技术对扇叶铁线蕨配子体发育和卵发生进行了研究。结果显示：（1）扇叶铁线蕨孢子黄褐色,四面体形,具三裂缝,孢子接种后4~7 d萌发,经丝状体和片状体阶段发育为心形的原叶体,成熟原叶体雌雄同株,在原叶体基部产生精子器,在原叶体生长点下方产生颈卵器。（2）切片观察表明,扇叶铁线蕨颈卵器产生于生长点下方的表面细胞（颈卵器原始细胞）,该细胞经2次分裂形成3层细胞,其上层细胞发育为颈卵器颈部壁细胞,中间细胞为初生细胞,它经2次不等分裂产生3个细胞——卵细胞、腹沟细胞和颈沟细胞;刚产生时,3个细胞紧贴颈卵器壁,随着发育,卵细胞和腹沟细胞之间产生了分离腔,同时在卵细胞上表面形成了染色深的卵膜;此后,颈沟细胞和腹沟细胞逐渐退化,在颈沟内产生大量不定形物质,受精作用观察表明,该物质能够吸引精子进入颈卵器。（3）连续切片观察发现,成熟卵细胞上表面卵膜中央具有受精孔,表明受精孔在同型孢子蕨类卵细胞中可能是普遍存在的。

The development of gametophytes and oogenesis of the fern Adiantum flabellulatum L.was studied using microscopical techniques.The spores are brown,tetrahedral and trilete.The spores germinate about 4~7 days after sowed.They develop into cordate prothallus through filament and plate stages.The adult prothallia,usually hermaphroditic,produce antheridia in the basal and archegonia near the apical notch of the prothallus.Section observation shows that the archegonium of the A.flabellulatum develops from a superficial cell,i.e.the initial cell of archegonium.The initial cell forms a tier of three cells by two divisions.The upper cell develops into an elongated neck.The middle cell,i.e.the primary cell,finally develops into a neck canal cell,a ventral canal 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,simultaneously,a layer of dark stained membrane is formed in the upper surface of the egg.Thereafter,the neck canal cell and ventral canal cell degenerate gradually and form a mass of amorphous materials in the cavity of the archegonium,which can induce the sperms entering the archegonium.Series sections show that a fertilization pore appears in the central region of the upper surface of the mature egg.The discovery of the fertilization pore may indicate that the pore occurs universally in the egg of the ferns.