The Formation Of Female Gametophyte And Embryogenesis In Pinus Yunnanensis Franch

The formation of female gametophyte and embryogenesis is one of the most important contents in gymnosperms embryology research. Pinus yunnanensis belongs to one of the generation of Pinaceae, which are widely distributed in southwest of China, is the pioneer tree species of afforestation of barren hills and material of the main tree species in southwest of China. So far, investigation on the embryology of Pinus yunnanensis lacks of systematization.This paper studied the formation of female gametophyte and embryogenesis of Pinus yunnanensis by paraffin section technique. The main results were as follows:The micropyle opened, dyad and linear tetrad in the depths of the nucellus in early April, and quickly produce functional megaspore, which entered into mitosis prophase and formed free nuclear. Cell walls began to form in the second year in late April. The female gametophyte formed in early May and the archegonium matured in late May, the number between 2 to 6, and plasmodements was not found around the egg nucleus in mature egg cell. Fertilization started in early June, and many protein vacuoles and a few vacuoles existed in mature egg cell before fertilizing. The number of protein vacuoles reduced and vacuoles increased and biggered gradually after fertilizing. After neck cells opened up, the sperm entered into the vacuole of archegonium, with sperm flagellum disappeared, and then sperm moved to egg nucleus. Pinus yunnanensis entered the stage of embryonic development in early June and lots of starch granules formed in the endosperm cell in early August. Embryos matured in late October. The embryonic development was the same as other plants of Pinaceae Lindl. These cells like beehive during the formation of female gametophyte were firstly observed in this study. There are 2--4 layers cells like beehive, and the shape were irregular. The innermost 1-2 layer cells had nucleus with monocyte and a little cytoplasmic. The inner surface of the cells’structure were different, some had cell walls and others closest female gametophyte had no cell walls and was open. The outside 1-2 layer cells had cell walls, with irregular shape, and no nucleus and cytoplasm. There were two layers in cells like beehive, with many nucleuses with thickening of cytoplasm are between the two layers. There were gaps among nucleuses, but did not sure whether there were cell walls around the nucleus.