The Embryo Sac: The Female Gametophyte. The classification is based on: The number of 9 ses or spore nuclei entering into the formation of embryo sac Thus embryo sac may be monosporic, bisporic or tetrasporic tyr; The number, arrangement, and chromosome number of the nuclei in the mature embryo sac. Unlock Content Over 83,000 lessons in all major subjects D. Formation of body of developing embryo. embryo sac The female gametophyte (an oval structure in the nucellus of the ovule) of flowering plants, formed by the division of the haploid megaspore nucleus, and the site of fertilization of the egg and development of the embryo. Amphitropous. The body of the ovule is very much curved that the embryo sac and the ovule itself take the shape of a horseshoe. The pollen grain is transferred by various agencies (wind, water, animals) to the stigma of the female flower, and, as in… Embryo sac is the female gametophyte of a flowering plant, consisting typically of a microscopic elongated sac that is situated within the ovule and contains eight nuclei in seven cells: it gives rise to the embryo and endosperm of the seed after fertilization. The embryo sac is only slightly curved. Bruce M. Carlson, in Reference Module in Biomedical Sciences, 2014. The two polar nuclei in the central cell ultimately unite, becoming the fusion nucleus. A yolk sac provides nourishment for an embryo until around 12 weeks of development when the placenta takes over. The funicle in this case is especially long that it creates a nearly full circle around the ovule whose micropyle is ultimately pointing upwards. A yolk sac is the earliest evidence that can confirm a pregnancy is developing in the correct location inside of the uterus, usually 3-5 days before an embryo is visible. The embryo usually develops a circulatory system by week 12, which is when the yolk sac ceases its own circulatory functions. There are three basic parts of a seed in the angiosperms: (a) an embryo, (b) a food storage or nutritive tissue, and (c) seed covering.. Embryo. MEDIUM. Drawing food for the developing cells. Yolk Sac. C. Formation of yolk sac. The embryo envelops a portion of the yolk sac, which protrudes with the umbilical cord from what will become the abdomen. the parts of a seed and their functions in seed and plant development. Embryo sac definition, the megaspore of a seed-bearing plant, situated within the ovule, giving rise to the endosperm and forming the egg cell or nucleus from which the embryo … Types of embryo Sac Development. The yolk sac, which is lined by extraembryonic endoderm, is formed ventral to the bilayered embryo when the amnion appears dorsal to the embryonic disk.In contrast to birds and reptiles, the yolk sac of mammals is small and devoid of yolk. Other articles where Antipodal cell is discussed: plant development: Preparatory events: …at the opposite pole, the antipodals, play a part in embryo nutrition in certain genera. The embryo folds laterally and again at either end, forming a C-shape with distinct head and tail ends. ... which will make contact with the endometrium and take part in establishing the embryo's means of receiving nutrition. Functions of Ovules Circinotropous. It consists of 6 haploid cells without cell walls (2 synergidae, 3 antipodal cells, and an egg cell) and 2 haploid nuclei (polar nuclei). First, a single cell in the diploid megasporangium (mega = large), located within the ovules, undergoes meiosis to produce four megaspores. 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