Morphology, Structure, Development And Systematics Of Actaea Asiatica Hara. (Ranunculaceae)

The anatomical structure, trancheary elements, flora morphogenesis and embryology of Actaea asiatica which is an endemic and monotypic genus of Ranunculaceae in East Asian were described in the present paper. We attempted to supply some new features on the determination of the systematic position of Actaea in Ranunculaceae.1. Anatomical Structures of ActaeaRoot: root tip is consisted of initial cells of calyptrogen,periblem and plerome;the root with diarched and tetrarched primary xylem;without secondary structure in root.Stem: The secondary structure in stem is similary to the primary structure in stem, and the vascular arranged in tapical "V".Node:the node is unilacunar and multi-traced.Leaf: The stomata of leaves are anomocytic type.The vascular bundles of the petiole are arranged in circle.The inferior epdermis cells are anomalistic.Ridge distributing on the upper epidermis cells of leaf.Flower: There are perianth,androecium and gynoecia on receptacle.The node of sepals is unilacunar and 2-traced,while the nods of petals and stamens are unilacunar and 1-traced.There is 1 carpel that is 3 traces in the basal.The configurations and vascular of stamens and petals are similar.2. The treachery elements in the xylem of Actaea asiaticaThe types of trancheary elements in the root and rhizome of the genera are varied.The major types include:Tracheary, tracheid-like vessels,fibriform vessels and typical vessels.The form of the perforation plates in the typical vessels are various,divide into several subtypes:scalariform perforation plates,reticulate perforation plates.mixed perforation plates and simple perforation plates.Lateral-wall perforation plates,multiple end wall and the membrane remnants are also observed in the secondary xylem.The distribution of the vessels in different organs of Actaea is difference.3. Floral morphogenesisThe initiation of floral organs is centripetal;the petals and the stamens are spiral ininitiation while are whorled in later development stage;the primordials of stamens and petals are homeosis,the petals are retarded;the carpel conduplicated at the early stage and from chair-shape to the mature stage. The stigma with inconspicuous style and papillary cells at the top of the carpel.4. EmbryologyThe features of the microspores and the male gametophyte of Actaea asiatica are: the young anther is tetralocular;the mature anther wall comprises the epidermis,the endothecium,2-3 middle layers and a glandular tapetum;microspore is simultaneous type;pollen tetrads are tetrahedral and cross type.Two-cells at the shedding stage of the pollen;The ovule of Actaea is anatropous,bitegmic and crassinucellate ovule;the chalazal functional megaspore developed into a polygonum type of embryo sac;the endosperm development of Actaea was the nuclear type.5. Systematic positionAccording to the characters of anatomy,treacheary elements,floral organogenesis and embryology of Actaea.We considered that Actaea should be an espiceally group in Trib Cimicifaga.