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

陆生植物的主要趋势是由同源孢子向异孢子演化，有大孢子和小孢子。异孢子比同孢子更有利于避免配子体自交，异孢子蕨类植物是由游动孢子蕨类植物进化而来，其次是种子植物由异孢子蕨类植物进化而来。在这项研究中，我们试图检验工作假说的有效性，即生物体避免自交的共同选择压力将迫使从同源到异源和种子习性的转变。我们重点研究了育种系统和授粉系统，并在不同的植物群体之间进行了比较。从日本和邻近地区的实地考察和文献研究中，我们观察到卷柏属和水杉属植物的大孢子表面附着着小孢子：结果表明，与胚珠或柱头上的花粉授粉相比，这是一种“孢子授粉”。我们收集了水仙属的大孢子，这将有助于研究“孢子授粉”是否发生在地质时代。在解剖学观察中，我们证实了卷柏属内胚层的解体形成了气道，并推测这种陆生异孔蕨类植物可能是水生的，类似于水生水生蕨类植物。进行了遗传分析，以确定水仙属的繁殖模式，在这种模式下，可能发生的自交是由于“孢子授粉”。结果正在调查中。对雌雄异株裸子植物中的一种例外--雌雄同株松树的繁殖系统进行了生殖物候观察。结果表明，由于保护作用，它有一个交叉系统。我们将雌雄异株和功能异株与原始被子植物的两性花和高等被子植物的两性花进行了比较，推测裸子植物向被子植物的进化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.