Development Of Male And Female Gemetophytes And Their Ultrastructure In Saxifraga Hirculus L

The alpine subnival plant is a kind of special circumstances (cold, strong wind, strong ultraviolet radiation, etc.) group, whose reproductive system face a great resistance. Our study is based on reveals the breeding mechanism of alpine subnival plant. In this paper, we used alpine subnival plant Saxifraga hirculus L. (Saxifragaceae) as materials, which were gathered from Glacier No.1,China.We did a series of studies on the development of female, male gametophyte and their ultrastructure of Saxifraga hirculus L by means of traditional paraffin wax section, scanning electron microscopy and transmission electron microscopy. The main results are this:1,Reveal the stamens'structural features and development process of microspore. The development of male gametes of Saxifraga hirculus L revealed that the anther is 4-sporangiate and the development of its anther wall is basic type.The anther wall is composed by epidermis, endothecium, middle layer and tapetum. The mature pollen grains are 2-celled type. We found abnormal pollen development.2,Describe the structural features of the pistil and dynamic process of megaspore from mononuclear embryo sac to eight-nucleate embryo sac The pistil has two carpels and two ovaries, each ovary contains tens to hundreds of ovule, the ovule is bitegminous and crassinucellate. The micropyle is formed by inner integument. Sporogenous cells develop into megaspore mother cell, megaspore mother cell undergo meiosis to form tetrad, the chalazal functional megaspore develop, and the remaining three micropylar megaspore degradation. Embryo sac development is Polygonum type. The mature embryo sac has seven cells and eight nuclei. Two central polar nuclei size is insignificant and not fusion, antipodal cells degenerate later.3,Illustrates the morphology of pollen. According to the observation of pollen by scanning electron microscopy, the Pollen is spherical; polar long 41.5um, equatorial axis length 37.5um; germination hole is tricolporate, the dicth is thick and deep, side apertures, non-equatorial zone; the polar regions is reticulate and the equatorial zone to be meshed.4,Reveal the cytoplasm Change characteristics during microspore development. Use transmission electron microscopy observe the microspore ultrastructure in Saxifraga hirculus L In the early and middle phase of microspore development there are abundant mitochondria and endoplasmic reticulum; After asymmetric division of microspores, the smaller reproductive cell and the larger vegetative cell are formed, the vegetative cell has large quantity of organelles, contains many starch grains and lipid bodies; the tapetal cells are metabolically active during the development of microspore, their organelles changes constantly, contains abundant mitochondria, endoplasmic reticulum and plastids, as the foundation for the development of two-cell pollen grain.5,Illustrates the function of each cell in the embryo sac and the changes characteristics of their cytoplasm. The mature embryo sac has seven cells and eight nuclei:an egg cell and two synergid cell formed egg apparatus, three antipodal cells and a central cell. The central cell is the largest cell in the Embryo sac, it has a large central vacuole and cytoplasm concentrated around the polar nuclei, two polar nuclei are in different size. The cell wall sometimes is thin or missing, where it stretches in contact with the synergid cell, and there find plasmodesmata. The synergid cell has high electron density cytoplasm, because it contains a rich complement of organelles. Rough endoplasmic reticulum are nomerous, mitochondria and lipid bodies were observed. The cell wall of egg cell is thin, there are many plasmodesmata where the egg cell in contact with the synergid cell antipodal cells,we indicate that they have a lot cytoplasmic exchange between them. Antipodal cells show high density of organelles, especially for rough endoplasmic reticulum, the mitochondrial are large and contain well developed cristae, so we think antipodal cells metabolic activity. There are also many vesicles there which transport nutrients to the embryo sac.All in all, Saxifraga hirculus L formed breeding mechanism that adapt to alpine subnival environment ensure the continuation of the offspring. Our study provides a theoretical basis for embryology research in Saxifraga hirculus L, and also offers a theoretical support for reproductive Biology...