银杏和苏铁类植物的生殖特征比较

银杏和苏铁类植物是现存种子植物中仅有的2个具多鞭毛游动精子的类群。自1896年Hirase和Ikeno分别发现银杏和苏铁类植物的游动精子以来,研究人员对它们的生活史、胚胎发育、系统演化等已进行了大量研究。本文综述了近年来银杏和苏铁类植物在生殖生物学方面的研究进展,比较了它们生殖特征的异同,并对它们间的亲缘关系进行了初步探讨。通过对一些演化上有重大意义的特征的比较,显示在雄配子体发育及种子发育方面苏铁类植物较银杏保留了更为原始的特征,而在雌配子体发育方面则较银杏更为特化;银杏和苏铁类植物均具有许多特有的结构特征,表明两者在进化过程中是平行发展的,在种系发生上不相关。

Review of Reproductive Characters in Ginkgo and Cycads

Ginkgo and cycads are the only two lineages bearing multiflagellated spermatozoids in all extant seed plants.Since the discovery of their flagellated spermatozoids by Hirase and Ikeno,the general morphology and anatomy,the life cycle and the systematic evolution of Ginkgo and cycads have been described in many reports.We compared the reproductive characters of Ginkgo and cycads based on literatures,and found that Ginkgo and cycads have many differences in embryo development.The cycads possess more primitive characters in male gametophyte and seeds development;while Ginkgo preserves more primitive characters in the female gametophyte.It suggests that Ginkgo and cycads might have undergone parallel development in evolutionary process since the divergence of their common ancestors and have no ancestral-descendent relationship in phylogeny.