Abstract
Embryo development is examined in Arundo formosana ultrastructurally and histochemically from fertilization to embryo maturity. During development, the zygote shows a polarity change in which the centrally located nucleus surrounded by most of the organelles shifts toward the chalazal pole. Early embryogenesis is of the Asterad type in that the cell divisions of the early proembryo are regular. The proembryo displays a continuous gradient of vacuolation from the highly vacuolated basal cells to the apical cells. The suspensor and the embryo proper can be clearly distinguished by cellular contents during development. During differentiation, the embryo proper shows dorsiventrality in that the dorsal and ventral regions become the scutellum and embryo axis, respectively. Large increases in amount of ER, lipid bodies, and protein bodies occur in the scutellum during embryo maturation. In the scutellum, lipids and starch accumulation proceeds basipetally, and storage protein accumulation proceeds acropetally. At maturity, the scutellar cells with centrally located nuclei are filled with lipid bodies and protein bodies except for procambial cells. Lipids are distributed throughout the embryo axis. Starch and storage protein are distributed in the leaf primordium, coleoptile, coleorhiza, and the ventral region of the mesocotyl. In cellular contents, the leaf primordium is similar to the coleoptile, except for the presence of protein bodies, and the ventral region of the mesocotyl is similar to the coleorhizal cells.
Published Version
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