Flowers of Araliaceae: structural diversity,developmental and evolutionary aspects

摘要

Within Araliaceae, at least four groups are recognized to have significant deviations from the typicaleuasterid flower groundplan: (1) Asian Schefflera clade (incl. Tupidanthus), (2) Plerandra group, (3)Tetraplasandra and (4) Osmoxylon. The main trends of flower structure variation are: reduction ofcalyx, increase in number of stamen whorls, increase of overall flower merism or only of stamennumber, increase or decrease of carpel number, congenital petal fusion with postgenital corolla clo-sure into a massive calyptra, appearance of flower disymmetry or asymmetry during flower develop-ment or even from its very beginning. Loss of polysymmetry is strongly correlated with increase oforgan number, at least in the androecium and in the gynoecium. Other trends show mosaic distributionbetween taxa studied. Our data suggest primitiveness of pentamerous tetracyclic polysymmetric flow-ers (possibly with dimerous gynoecium) in Araliaceae and multiple losses of this floral constructionin the evolution of the family. Multistaminate and multicarpellate flowers are clearly derived types inAraliaceae.