阔鳞瘤蕨(水龙骨科)卵细胞发育超微结构观察

Ultrastructural Observations on the Egg Development of the Fern Phymatosorus hainanensis(Polypodiaceae)

水龙骨科是蕨类植物中最进化的类群,该文采用超微技术对水龙骨科的阔鳞瘤蕨(Phymatosorus hainanensis)卵发育过程进行观察,以完善薄囊蕨植物卵发生的资料,为揭示蕨类植物的有性生殖及演化机制奠定基础。结果表明:(1)幼卵、颈沟细胞、腹沟细胞通过胞间连丝紧密连接。(2)发育过程中,卵与腹沟细胞之间细胞壁显著加厚,将卵细胞与腹沟细胞隔离。(3)在壁的下方产生分离腔,内含大量不定形物质,但卵细胞与腹沟细胞在中间处始终相连。(4)分离腔中的不定形物质沉积在卵细胞质膜外形成了一层加厚的卵膜,而在连接区(孔区)处不形成卵膜,该位置最终形成了受精孔。(5)卵细胞核变得高度不规则,近成熟时卵核产生了大量的核外突。

Polypodiaceae is the most evolutionary group in the ferns.However,the egg development in this group is less studied.The present investigation chooses the fern Phymatosorus hainanensis of Polypodiaceae,to examine the detailed development of the egg.Ultrastructural observations indicate that：（1）The young egg,the ventral canal cell and neck canal cell are closely connected with each other by plasmadesmata.（2）During egg development,the cell wall above the egg become obvious thickened and then a separation cavity,which contains plenty of amorphous materials,is formed beneath the wall.（3）A connection region persistently connects the egg and the ventral canal cell in the central area of the upper surface of the egg.（4）An egg envelope is formed by deposition of amorphous materials in the separation cavity on the outer surface of the plasmalemma.The egg envelope was not formed across the connection region;instead,a fertilization pore was formed.（5）In the later stage of oogenesis,the egg nucleus becomes irregular in outline and produces extensive evaginations.The present investigation provides new data on oogenesis of the ferns,which contributes to understanding of the cytological mechanism of the sexual reproduction of ferns and their evolution.