濒危植物瑶山苣苔的大小孢子发生和雌雄配子体发育研究

利用石蜡切片技术对瑶山苣苔大小孢子发生、雌雄配子体发育及胚胎发育进行了细胞学观察,结果表明:瑶山苣苔胚珠倒生,单珠被,薄珠心,具珠被绒毡层。大孢子母细胞减数分裂形成的四分体呈直线排列,合点端的大孢子发育为功能大孢子,其余3个大孢子退化,胚囊为单孢子发生的蓼型胚囊发育方式。花药为四囊形,花药壁由外到内依次为表皮、药室内壁、中层和腺质绒毡层,小孢子形成时胞质分裂为修饰性同时型,小孢子四分体排列方式为四面体形,成熟花粉为2核细胞。胚乳发育为细胞型,在胚的发育过程中被吸收耗尽。瑶山苣苔大小孢子发生和雌雄配子体发育基本正常,不是导致其濒危的原因。但瑶山苣苔果实成熟时,胚仅发育至球形胚时期,需要经过一定时间休眠才能完成形态后熟,表明胚未发育完全可能是该物种天然更新困难的原因之一。

Sporogenesis and Gametogenesis on Endangered Dayaoshania cotinifolia

To explore the possible endangered embryology causes of Dayaoshania cotinifolia,the paraffinsection method to observe mega-microsporogenesis,development of female and male gametophyte,andembryogenesis was employed.The main results as follows:The ovules were anatropous,single integument,thinnucellus,and with an integument tapetum.The megaspore mother cell had undergone meiotic divisions anddeveloped into a linear tetrad.The chalazal megaspore of the tetrad was functional one and developed into aPolygonum type embryo-sac,another 3 megaspores degenerated.The anther was tetraposiform,the anther wallwas composed with an epidermis,endothecium,two-layered middle layer,and a glandular tapetum.In themeiosis of microsporocyte,cytokinesis was a modified simultaneous type.The tetrads were tetrahedral andmature pollen grain was two-celled.The development of endosperm was cellular type and exhausted duringembryo development.The process of the mega-microsporogenesis and development of female and malegametophyte of D.cotinifolia were normal,which was not the cause of its endangerment.The embryo developedto the globular embryonic stage at ripe fruit,the morphological after-ripening process of the embryo could becompleted after dormancy.The undeveloped embryo might be one of the reasons for the difficulty of naturalregenerates naturally.