Studies of reproductive morphological characters and early evolution in monocots in the light of molecular information

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For better understanding of monocot relationships based on molecular data as well as of early evolution in monocots, reproductive morphological characters were investigated using basal monocots and related taxa. Major findings are as follows. Acoraceae (Acorales) have an integumentary obturator (as autapomorphy) and a nucellar obturator as a plesiomorphy. Contrary to previously known information, Araceae (Alismatales) have the cellular type of endosperm development. Thus, evolution is likely to have occurred from the cellular to the helobial type, and from the heobial to the nuclear type in Alismatales. Nartheciaceae (Dioscoreales) have an inferior ovary and a septal nectary as plesiomorphies in the family. The inferior ovary is a synapomorphy of eumonocots, but a reversal from the inferior to the superior ovary occurs many times. The septal nectary, which is prevalent in monocots (except in Acorales), is lost three times in evolution of monocots. Besides, anther wall formation mode and seed structure (seed coat and perisperm) were also discussed in relation to monocot evolution.