木兰目花器官形态多样性与演化

木兰目属于被子植物的核心分支之一，具有代表所有被子植物分支的祖先状态的性状，并与单子叶植物有系统发育上的关系，是研究被子植物起源和早期演化的重要类群。木兰目花的形态变异很大，甚至在同一科（属）中表现出多种变异，对各种变异类型花的形态与结构多样性的正确认识是探讨木兰目各类群的分类及演化关系的重要基础，对这些类群同一性状的演化系列进行比较研究，从而探讨花的结构、功能及在整个被子植物中的演化式样意义重大。本项目采用显微切片、扫描电镜和激光共聚焦等技术，对木兰目各代表类群花的形态、结构和发育过程进行全面、系统的研究，正确认识花各部的形态、结构特征及器官的个体发育过程，阐明花部结构的同源性及形态变异的本质，结合分子系统学研究结果，揭示花部特征的系统分类学意义，探讨花部各性状的演化式样及类群的系统发育，为深入研究早期被子植物花的形成与演化提供重要基础资料。

Magnoliales were long thought to be 'the most archaic existing order of flowering plants'. However, recent higher-level phylogenetic analyses have refuted the Magnoliales as the most primitive angiosperms. Nevertheless, Magnoliales remain one of the most important lineages in the early radiation of angiosperms, and are located in the magnoliid grade that is basal to eudicots and monocots. The taxa assigned to Magnoliales have varied considerably in recent classification systems. However, recent progress in angiosperm phylogenetics has led to a new, stable circumscription of the order as a monophyletic group of six families, including Annonaceae, Degeneriaceae, Eupomatiaceae, Himantandraceae, Magnoliaceae and Myristicaceae. The presumed primitive characters in Magnoliales include simple, entire leaves with pinnate venation and monosulcate pollen, which have been considered as the ancestral state for the large clade containing the Chloranthaceae, Ceratophyllaceae, monocots, and eudicots. Therefore, Magnoliales appear the phylogenetic relationships with monocots, and play the important role in the study of origin and early evolution of angiosperms flower. Floral structure is generally conserved with four main organ types (sepals, petals, stamens and carpel). However, the variation on this theme is extensive, particularly in Magnoliales, which the dramatic floral diversities even appear within a family or a genus. The types of variation include the color, arrangement, number or size of floral organs, abortion of organs, radial versus bilateral symmetry, whorled or spiral phyllotaxis. Understanding the floral diversity of Magnoliales is therefore key to deciphering the essence of floral diversity in angiosperms. In this project, the applicant is going to conduct extensive researches on the floral morphology, structure and ontogeny on the selected taxa by using paraffin section, semi-thin section, scanning electronic microscope (SEM) and laser scanning confocal microscope (LSCM) technology. The aims of the project are: providing fundamental knowledge on the floral variation of morphology, structure and phyllotaxis; understanding the nature of floral diversity, especially on the degenerated or sterile organs; evaluating the systematic value and developmental patterns in floral characters under the well-supported phylogenetic frame on Magnoliales and the basal angiosperms as well.