Developmental and Structural Section
Iwamoto, Akitoshi , Izumidate, Ryoko .
Floral and vegetative development in Ceratophyllum demersum (Ceratophyllaceae).
Ceratophyllum has been placed in a key position within the phylogeny of Angiosperms based on the results of molecular analysis. Recent analyses reported a sister group relationship of Ceratophyllum to the eudicots. There are other possibilities, in particular, a sister group relationship to the monocots is probable. Therefore, the morphological features of Ceratophyllum are important for elucidating the phylogenic position of the genus, but some of them remain to be observed, especially anatomical observations are necessary. In this study, we observed in detail the developmental anatomy of lateral organs initiated at nodes of Ceratophyllum demersum, including vegetative buds, staminate and pistillate flowers. The primordium of vegetative buds was initiated at every node with a subtending leaf, while floral primordia were not found at every node and lacked a subtending leaf. The vegetative buds were often produced singly at each node, but all flowers were accompanied by vegetative buds at the same node. These observations imply that the vegetative buds are derived from main axillary buds, and their accessory buds develop into the flowers. The staminate flowers of C. demersum are composed of more than 10 stamens and are surrounded by more than 10 bracts (sometimes regarded as tepals). The pistillate flowers are composed of one pistil and are surrounded by more than 10 bracts. The staminate floral apex developed bract primordia first, then stamen primordia. In the early development stages, the bract and stamen primordia were initiated on the abaxial side of the floral apex and only later on the adaxial side (unidirectional). In the pistillate floral apex, the bract primordia also showed unidirectional initiation. The developmental feature are in common with the flowers of Acorus, the most basal monocot, and the Piperales, a group considered to be close to monocots, which may imply a closer relationship between Ceratophyllum and monocots than with other possible sister groups.
Ceratophyllum is considered to be placed in a key position within the phylogeny of Angiosperms. There are two probable positions, the sister group to monocots and the sister group eudicots. The detailed analysis of floral and vegetative development of Ceratophyllum may lead to the determination of its phylogenic position and a better understanding of floral and vegetative evolution in the angiosperms.
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1 - Tokyo Gakugei University, Department of Biology, 4-1-1 Nukui-Kita, Koganei, Tokyo, 184-8501, JAPAN
Presentation Type: Oral Paper:Papers for Sections
Location: 551A/Convention Center
Date: Tuesday, August 3rd, 2010
Time: 1:30 PM