Ranunculaceae The Cohosh Family (cimicifugeae) Flower Development And Vascular Structure

The tribe Cimicifugeae in Ranunculaceae contains 6 genera:Cimicifuga,Beesia,Actaea,Souliea, Eranthis and Anemonpsis.The development of inflorescences and flowers,the perforation plate of vessels and the vascular system of Cimicifugeae were described in the present paper with the aim to elucidate the systematic position of the tribe and the phylogenetic relationship among the genera. The main results are summarized as follows:1.Floral Morphogenesis and DevelopmentInflorescences and flowers of 4 species from Cimicifuga,souliea,Actaea and Beesia of Cimicifugeae were studied with a scanning electron microscopy.It is showed that Beesia has some primitive characters and is closely related to other genera of Cimicifugeae:the floral organs initiate spirally and the phyllotaxis is spiral;the sepal primordia are lunular in shape and truncate at apex, the stamen primordia are hemispherical in shape and rounded at apex;petals absent;the single carpel is conduplicate.It is strongly supported that Beesia is primitive in Cimicifugeae.Souliea,Actaea and Cimicifuga share some common features on inflorescence and floral developmentent:The initiation and early development of inflorescences are similar;all floral organs are initiated centripetally;the sepal primordia are lunular in shape,the petal,stamen primordia are hemispherical in shape;the petal primordia developed more slowly than the stamen primordia;the 1-2(3)carpels are conduplicate.However,there are obvious differences based on the present study: The terminal flowers develop more rapidly than the lateral flowers in Souliea and Actaea in later satges;the intiation and phyllotaxis pattern of floral organs in the three genera varies with the number of floral organs;the developmental process of petals in Actaea undergoes the feature of stamens and without nectary,but petal with a nectary in Souliea and Cimicifuga;the stigmatic tissue is different in the three genera.The diverse characters on inflorescence and floral ontogenesis indicate Souliea,Actaea and Cimicifuga should be treated as separate genus,while Souliea and Actaea share many special features.2.Vascular SystemThe vascular system of Cimicifuga,souliea,Actaea and Beesia in Cimicifugeae is bicollateral bundle and the xylem is concave at the side touching to the phloem and shows V-shaped appearance, just in Beesia the "V" is not obvious.The bundle sheath is on the outside of the phloem and similar to most of Ranunculaceae.It is indicated that Cimicifuga,souliea and Actaea have close relation, and Beesia has some common features with them but also has certain differences.The vascular system of Eranthis is collateral bundle and the fibrous cell groups surround the bundle,it is strongly supported that Eranthis is special in Cimicifugeae.3.Perforation plate of vessels in CimicifugeaePerforation plate of vessels of 3 species from Cimicifuga,Beesia and Eranthis of Cimicifugeae were studied with a scanning electron microscopy.The results combined with the reports of Souliea and Actaea which have been studied by other people showed that they share some common features on perforation plate of vessels:(1) the simple perforation plate exist in each genera;(2) the transition perforation plate exist in each genera;(3) the mixed perforation plates exist in Cimicifugeae except Eranthis.However,there are obvious differences:Eranthis contain only simple and scalariform perforation plates,which indicate it is evolutionary;the simple,transition perforation plate and different mixed perforation plates in Cimicifuga,Beesia,Souliea and Actaea showed their close relation and transition on the level of evolution.4.Cladistic Analysis and Systematics Relationship5 genera in Cimicifugeae are cladistically analyzed based on character of floral morphogenesis, characters of vessel elements and vascular system and the former date,using Trollius and Helleborus as out group.The Cimicifugeae is a monophyletic group,and Beesia and Eranthis should be included in this tribe.It is indicated that Cimicifuga,souliea and Actaea have close relation,but should be treated as separate genus.