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Unformatted text preview: at the end of the embryo sac (opposite the micropyle); two nuclei in the central region of the embryo sac, termed the polar nuclei ; and three nuclei at the micropylar end of the embryo sac, consisting of two synergids surrounding an egg. During the process of double fertilization , one sperm nucleus fuses with the egg to form a zygote (2n), which eventually divides by mitosis to become the embryo. The second sperm nucleus does not degenerate (unlike fertilization in conifers), but instead fuses with the two polar nuclei to form the endosperm nucleus (3n) . The endosperm nucleus then divides to form endosperm tissue, which provides nutrition for the developing embryo. The fertilized ovule is termed a seed. Seeds remain inside the ovary, which develops into the fruit (see Section H). Draw an embryo sac and label all of the nuclei visible....
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- Fall '11