Study of the evolution of heterosporous plants with respect to pollination and breeding systems

陆生植物的主要进化趋势是由同孢子生殖向大孢子和小孢子的异孢子生殖进化。据解释，异孢子生殖是有益的，同源孢子生殖相比，在避免配子体自交，异孢子蕨类植物从游动孢子的，其次是种子植物，从异孢子蕨类植物进化而来。在这项研究中，我们试图检查的有效性的工作假设，共同的选择压力，生物体，以避免自交，将迫使过渡从同孢子生殖到异孢子生殖和种子的习惯。重点介绍了植物的繁殖系统和授粉系统，并对不同植物类群的繁殖系统和授粉系统进行比较。通过在日本及邻近地区的野外调查和文献研究，我们观察到卷柏属（Selaginella）和柳叶菜属（Isopropyla）的小孢子附着在大孢子表面上。结果：与胚珠或柱头上的花粉（=小孢子）授粉相比，我们认为是“孢子授粉”。我们收集了大孢子的Isoptera，这将是有用的，以检查是否“孢子授粉”发生在地质时代。在解剖学观察中，我们证实了气道的形成与卷柏内胚层的解体，并建议这种陆生异孢子蕨类植物可能是水生的，像Isoptera和异孢子水蕨类植物。通过遗传分析，确定了Isobacillus的繁殖方式，即自交可能是由于“孢子授粉”。“结果正在调查中。对雌雄异株裸子植物松属植物的生殖系统进行了观察。结果表明，该属存在一个由雄性先熟引起的杂交系统。通过对原始被子植物（Ambrella，Nymphaeales）和高等被子植物的雌雄同体花与功能性雌雄同体花的比较，推测在裸子植物向被子植物进化的过程中可能发生了显著的变化。

Land plants have the major trend of evolution from homospory to heterospory with megaspores and microspores. It is interpreted that heterospory is beneficial compared to homospory in avoidance of gametophytic selfing and that heterosporous pteridophytes evolved from zoosporous ones, followed by seed plants that evolved from heterosporous pteridophytes. In this study, we attempted to examine the validity of the working hypothesis that the common selective pressure for organisms to avoid selfing would force transitions from homospory to heterospory and to seed habit. We focused on the breeding system and pollination system and compared them among different groups of plants. From field researches in Japan and adjacent regions and publication research, we observed microspores attached on the surface of megaposres in Selaginella and Isoetes : Results suggestged "spore pollination," compared to pollination with pollen (=microspores) on ovules or stigmas. We collected megaspores of Isoetes, which would be useful to examine whether "spore pollination" occurred in geological times. In anatomical observations, we verified that aerial canals form with disintegration of endodermises in Selaginella and suggested that this terrestrial heterosporous pteridophyte might have been aquatic, like Isoetes and heterosporous water ferns. Genetic analyses were made to determine the reproductive mode of Isoetes, in which selfing might occur due to "spore pollination." Results are under investigation. A reproductive phonological observation was made to reveal the breeding system of the monoecious Pinus, one of exceptions in dioecious gymnosperms. Results suggest that it has a crossing system, due to protandry. We compared the dioecy and functional dioecy with the hermaphrodite flowers of primitive angiosperms (e.g. Ambrella, Nymphaeales) and advanced ones, and implied that remarkable changes might have taken place during the evolution from gymnosperms to angiosperms.