依兰(番荔枝科)雌配子体发育研究

Female gametophyte development of Cananga odorata(Annonaceae)

荔枝科是被子植物的基部类群之一,依兰属是番荔枝科较为原始的类群,其有性生殖过程,特别是胚胎发生与发育的研究结果,可以补充被子植物胚胎学原始特征的相关基础资料。该研究利用常规石蜡切片技术,对依兰胚珠、大孢子和雌配子体的发生发育过程进行了观察。结果表明:依兰的胚珠为倒生胚珠、厚珠心、三层珠被,第三层珠被(中间珠被)发生在大孢子母细胞时期,于外珠被与内珠被之间、胚珠合点端两侧发生并隆起;雌配子体为蓼型。此外,依兰的个别胚珠中存在双雌配子体现象,且两个雌配子体均由大孢子母细胞发育而来,大小、形状相近,呈线形排列。该研究结果对于揭示原始被子植物胚胎发育特征具有重要意义。

Annonaceae is one of the basic groups of angiosperms and Cananga is a primitive genus in it. The study on its embryo development is of great significance to reveal the embryological characteristics of the basic angiosperms. In this study,the ovule,megaspore and female gametophyte development of C. odorata were studied with the traditional paraffin section method. The results showed that the ovules of C. odorata were anatropous,assinucellate and tritegmic. The third integument（ or middle integument） occured in the megaspore mother cell stage,initials and enlarges between the inner and outer integuments,on the two sides of the chalaza end. The development of the female gametophyte conformed to the polygonum type. Occassionaly two linear arranged female gametophytes were found in the same ovule and both female gametophytes were developed from megaspore mother cell,with similar size and shape. This study on sexual reproduction process,especially on the process of embryogenesis and development will add some basic information about the primitive embryological features of angiosperms.