Morphology, Structure, Development And Systematics Of Sinofranchetia (Lardizabalaceae)

The anatomical structures, leaf ontogeny, flora morphogenesis and embryology of Sinofranchetia which is an endemic and monotypic genus of Lardizabalaceae in China were described in the present paper. We attempted to supply some new features on the determination of the systematic position of Sinofranchetia in Lardizabalaceae. 1. Anatomical Structures of SinofranchetiaRoot: root tip is consisted of initial cells of calyptrogen, periblem and plerome; the root with diarched primary xylem; the secondary structure is similar to other dicotyledonous; five types of vessel perforation were recognized in these species: (1) the simple perforation plate, (2) the scalariform perforation plate, (3) the simple-scalariform perforation plate, (4) the reticulate perforation plate, (5) the simple-reticulate perforation plate; The separate fiber are very common in the root.Stem: the node is trilacunar and 3-traced, the vessels are as same as in the root; the crystals are founded in the parenchymatous cells of core.Leaf: The stomata of leaves are actinocytic, the vascular bundles of the petiole are arranged in circle.Flower: The nodes of sepals, petals and stamens both in male and female flowers are unilacunar and 1-traced. There are three sterile carpels that are with 2-3 traces in the male flowers. There are three fertile carpels with 2-3 traces and sometimes three sterile ones without vascular supplying. The morphology, the way of dehiscence of anthers and the pollens of the stamens in the female flowers is as same as that of in the male flowers, therefore the so-called female flowers of the genus mightbe bisexual in morphology.2. The leaf ontogeny of SinofranchetiaThe leaf primordia are integrated at the stage of initiation. Two lateral leaflets primordial initiate from the each side of the leaf primordium later. The remained terminal part forms the primordium of the terminal leaflet. The development type of leaf primordium is heteroacron.3. Floral morphogenesisThe initiation of floral organs is centripetal; the sepals, petals and the stamen are spiral in initiation while are whorled in later development stage; the 3 carpel are not initiated at the same time; the stamen and petal(nectary leaf) are not initiated from the common primordia; the petals are retarded; the carpel conduplicated at the early stage and form the stigma with inconspicuous style at the top of the carpels; the inner integument derived from the epidermis cells of lateral sides of the funicular; the outer integument derived from the funicular later, the outer one is semiannular at early development stage.4. EmbryologyThe features of the microspores and the male gametophyte of sinofranchetia (Lardizabalaceae) are: the young anther is tetralocular; the mature anther wall comprises the epidermis, the fibrous endothecium, 2-3 middle layers and a secretory tapetum; cytokinesis is simultaneous; pollen tetrads are tetrahedral; the pollen grains of male flower are tricolpate and two-celled at the shedding stage; the sterile and mature pollens can be found in one locular, the mature pollen grains of female flower are three-colpate and two or three-celled at the shedding stage.The ovule of sinofranchetia is anatropous, bitegmic and crassinucellate; the chalazal functional megaspore developed into a polygonum type of embryo sac; the endosperm development ofsinofranchetia was of the Nuclear type. 5. Systematic positionAccording to the characters of anatomy, floral organogenesis and embryology of Sinofranchetia, such as five types of vessel, the mature pollen in stamen of female flower, the spiral initiation of perianth, the stamen and petal are not initiation from the common primordia, the retarded petal, we considered that Sinofranchetia should be a basic group and might be at least in the same evolutionary level with Decaisnea in the family.