angiodevelop213 - Flowering Plants Early Growth and...

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Flowering Plants: Early Growth and Development - 1 Following the double fertilization in the flowering plants, the zygote develops into the embryo, the endosperm nucleus into the endosperm tissue, the embryo sac wall and integuments of the ovule into the seed coat and the ovary and accessory tissue into the fruit. In this section we will discuss the development of the embryo, seed and fruit maturation, dispersal and germination. Embryo Development The first division of the zygote produces a small proembryo cell and a larger basal cell that develops the stalked suspensor, which elevates the developing proembryo into the endosperm tissue. Zygote (within the embryo sac) | First Division | || Upper cell Lower cell Proembryo Basal cell of the Suspensor Mass of cells Suspensor Stalk (surrounded by endosperm) Suspends embryo into endosperm | Proembryo, divided into 3 layers Protoderm ---> Surface Tissues Procambium ---> Vascular Tissues Ground Meristem ---> Ground Tissues | The embryo takes on the shape of an axis with meristems at both ends. The embryo meristems are the apical shoot meristem and the apical root meristem, from which structures of the shoot system and root system will ultimately develop. In addition, if a dicot, 2 bumps appear near the anterior; these are the 2 cotyledons, characteristic of dicot embryos. The cotyledons rapidly elongate, and the embryo is divided into regions, with respect to the cotyledons. The region above the attachment of the cotyledons is the epicotyl, which contains the apical shoot meristem The region below the attachment of the cotyledons is the hypocotyl that ends with the radicle, containing the apical root meristem. Typically the embryonic axis will have to fold, to fit within the embryo sac Endosperm may or may not be absorbed into the cotyledons. It may be consumed completely in the maturation of the embryo, or some may remain for germination. Some monocot cotyledons become modified into a coleoptile, surrounding the epicotyl and hypocotyl, and the coleorhiza, surrounding the radicle. This is common in grasses.
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Flowering Plants: Early Growth and Development - 2 Embryo Development in Capsella , Shepard’s Purse, an Eudicot Fertilization 2-cell Embryo Young Embryo Heart Embryo Cotyledon Stage Bending Embryo Mature Embryo Embryo Development in Lily, a Monocot
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Flowering Plants: Early Growth and Development - 3 Seed and Fruit Formation and Dispersal While the embryo is developing within the embryo sac, changes are also occurring in surrounding tissues. The ovule integuments and the embryo sac wall form the seed coat, which will protect the embryo until germination. The mature seed is comprised of the embryo, endosperm nutrient tissue and seed coat. In some seeds, notably legumes, the cotyledons will absorb the endosperm tissue, becoming "fleshy", so that the bulk of the seed is endosperm. In many monocots, the cotyledon will be modified to form a coleoptile, which surround and protects the epicotyl and the coleorhiza that protects the radicle. In some grains, the cotyledon forms a nutrient-rich scutellum surrounding the embryo for germination. Nutrients also pass from the endosperm through the scutellum to the embryo.
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angiodevelop213 - Flowering Plants Early Growth and...

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