水曲柳大小孢子发生、雌雄配子体发育及其系统学意义

Development of macrospore and microspore, male and female gametophytes of Fraxinus mandshurica Rupr. and its phylogenetic significance

通过石蜡切片对水曲柳孢母细胞减数分裂和雌雄配子体发育过程进行观察,揭示大、小孢子发生和雌、雄配子体发育的解剖学特征,并通过与相关类群的胚胎学特征比较探讨其系统学意义.结果表明:水曲柳花药4室,药壁发育属双子叶型,腺质绒毡层,小孢子母细胞减数分裂为同时型,成熟花粉为2细胞型.子房2室,每室2个倒生胚珠,具单珠被,薄珠心.大孢子母细胞减数分裂形成的4个大孢子呈直线形排列,其中合点端的大孢子具备继续发育的功能.蓼型胚囊.其雄蕊先熟,散粉时,雌配子体还未发育成熟,处于大孢子母细胞减数分裂阶段.从目前雌、雄配子体形成和发育的资料来看,木犀科的胚胎学特征与玄参目较为接近,与龙胆目系统学关系较远,并就它们的胚胎学特征的系统学意义进行了讨论.

The meiosis of megaspore and microspore mother cells and the developmental processes of male and female gametophytes in Fraxinus mandshurica Rupr. were observed by the paraffin sectioning method. Their embryological characteristics were revealed and its phylogenetic significance was discussed by comparison with the relative genera. The results indicate that F. mandshurica is a dioecious tree species; its anthers have 4 microsporangiates, and the development of anther wall is of dicotyledonous type and the tapetum belongs to glandular type. In the meiosis of microsporocyte, cytokinesis is simultaneous. Mature pollen grains are 2- celled. The ovary has 2 locules and there are 2 anatropous ovules in each locule. The ovule is unitegmic and tenuinucellatae. The meiosis of megaspore mother cell forms a linear tetrad, and the chalazal megaspore is the functional one. The development of embryo sac is of polygonum type. Flowers are protandrous. When pollen grains shed, female gametophytes have not matured yet and still in the meiosis stage of megasporocyte. The embroyological comparison suggests that the embryological characteristics of Oleaceae are more similar to Scrophulariales than to Gentianales.