Embryological Studies Of Aspidistra Retusa K.Y.Lang Et S.Z.Huang

Aspidistra retusa K. Y. Lang et S. Z. Huang, which belongs to the genus Aspidistra Ker-Gawl. of the tribe Convallarieae in the family Liliaceae, is a perennial and evergreen plant and has certain ornamental and curative exploitation value. As a comparatively original and widely distributed species in Sect. Trilineares G. Z.L of Aspidistra, A. retusa has typical characteristics of its genus. In the past, there are many researches about its chromosome number, karyotype, palynology characteristics, microstructural of leaf and fruit surface, chemical constituents and its molecular systematics.Genus Aspidistra is a big genus in Liliaceae and Convallarieae, which has very typical features of China and Guangxi in terms of distribution. This genus occupies an important position in classification system of Liliaceae. The studies of it have scientific significance and local characteristics in the field of utilization and protection of plant biodiversity as well as the studies of plant system and evolution. Deep and systematic studies were completed in many areas including flora, geographical distribution, vegetation types, habitats of plant, distribution and characteristics of existence environment, evolution trend of morphology, cytology and palynology. But we haven't seen any study about the embryology of any species of Aspidistra so far.The aim of this thesis is to provide more embryology information of Genus Aspidistra to solve the problems of its position in evolution system and to advance its breeding, protection and sustainable utilization. This research studies the field of embryology, seed and seedling morphology of Aspidistra. Based on these studies, we have made a comparison between A. retusa and Convallaria majalis L..First,after studying A. retusa from the perspective of embryology we get the following results.1. A. retusa is hermaphroditic, asynchronous dichogamy, protandry and reverse herkogamy. As to this kind of plant, mega-microsporogenesis and the development of female-male gametophyte in it is unsynchronous, so does the development approach of flowers of the same plant. All these characteristics are beneficial to improve the efficiency of pollening, decrease the probability of selfing and increase the probability of fruiting.2. The superior ovary was trilocular with axile placentation. The forms of carpel and placenta are more evolutionary in Liliaceae. The style is open and there are canal cells in it, which is common in Liliaceae.3. The anther was 4-sporangiate and the mature pollen grains were of 2-celled type. The microspore mother cells underwent meiosis and the cytokinesis was successive which resulted in the formation of isobilateral and occasionally tetrahedral tetrads. The cell of glandular tapetum would become binucleate or multinucleate at the later stages of its development. Because the development of tapetum accords with a normal process and the tapetum can offer enough nutrition to microspore, the mature pollen abortion rate is law. Those characteristics accords with typical characteristics of the development of microspore and the female gametophyte in Liliaceae.4. The ovule is orthotropous in early stage but anatropous after maturation. It is biteguminous and crassinucellate. The micropyle was formed by the inner integument. The study of A. retusa has proved that its ovule has many primitive characters.5. After the meiosis phaseâ… of megaspore mother cell, the cell at micropylar end is divided horizontally and finally disappear. At that time the cell at chalazal end is divided longitudinally and only functional one remains. The ovule at the tetrad stage is arranged in the shape of T. There are eight nucleuses in an mature embryo sac. The development of embryo sac was of the Polygonum type.6. There is endosperm in the seed. The seedling is hypogeal has a short neck. The cotyledonary sheath is short, whose upper edge uauslly grow into a ligular sheath. The haustorium is rod-like. The hypocotylis is not obvious. Theprimary leaf looks like a bar. The type of seedling is the Reineckea.Second,according to the comparative embryology study between A. retusa and Convallaria majalis L., we analyze their relationship and come to the following conclusions.From the existing data of Convallarieae, the process of microsporogenesis and the development of male gametophyte in C. majalis is almost the same as that in A. retusa. They are also the same in terms of the type of placenta and the arrangement and maintain time of antipodal cell. Both of them have T shape megaspore tetrad and a functional megaspore at chalazal end.The difference between them was mainly in the following aspects.1. There are two layers at the middle layer of A. retusa anther wall, one of which develops fibular thickenings at later stage. But there is only one layer at the middle layer of C. majalis and it will disappear when the pollen mature. 2. The development of embryo sac in A. retusa falls into the Polygonum type. The cell at micropylar end is divided horizontally and finally disappears, while the cell at chalazal end is divided longitudinally and only functional one remains. Only one functional cell develops into the mature embryo sac. A. retusa has monosporic embryo sac. But the development of embryo sac in C. majalis is of the Allium type or the Endymion type. The disintegrated megaspore cell is at chalazal end and the functional one is at micropylar end. Or the disintegrated megaspore cell is at micropylar end and the functional one is at chalazal end. C. majalis has bisporic embryo sac.Based on these, we can know that both A. retusa and C. majalis have displayed many primitive characters. Both of them have two shapes of microspore tetrads and have two-celled mature pollen grains. They are the same at the type of nucellus and other aspects. On the other hand, the Polygonum type embryo sac of A. retusa shows that it is more primitive than C. majalis. Therefore, both of them are not quite developed in Convallarieae, but C. majalis is in a more evolutional position then A. retusa.