Abstract
Before anthesis, rice antipodal cells are located between nucellar cells and a central cell, and have a large-sized lobed nucleus and many cell-wall ingrowths abutting the nucellar cells. An outstanding feature in the cytoplasm is the appearance of a multilayered, concentric configuration in endoplasmic reticula. They are constituted of several rings which enclose a component of cytoplasm or a plastid in the center. Two or three rings are connected with each other through a small joint, and as a result, a continuous lumen is ensured. These complicated figures of endoplasmic reticula probably come apart just after anthesis and rearrange into a great number of singular cisternae, of which features have been illustrated. From these circumstances, it is concluded that the configuration of endoplasmic reticula in antipodal cells strictly depends upon the developmental stages of the embryo sac. Furthermore, the dilation of lumens is observed on the singular cisternae located near the cell wall separating the central cell. The deposition and dilation of the singular segments are meaningful in relation to the nutrient transfer from the antipodal cells into the central cell. Finally, the higher activity of rice antipodal cells is indicated from the ultrastructural viewpoint. Additionally, the configurational change of endoplasmic reticula is discussed in the context of metabolic activities in the antipodal cells of rice and other plants.
