Ultrastructure of Nucellus and Endosperm ofDiplotaxis ErucoidesDuring Embryogenesis

SUMMARYDiplotaxis erucoides endosperm receives the degenerated contents of nucellar cells. In the degenerating nucellar cells at first ER dilations can be seen; later the ER cisterns become anastomised and split the cytoplasm into small islands. Nucellus cell-walls also degenerate and all the cell contents are incorporated in the endosperm. The endosperm can be divided into two portions: one surrounding the central vacuole, embryo and suspensor, the other lying in contact with the nucellus. The ultrastructure of these zones is shown during different periods of embryo development before and after endosperm cellularization; this phenomenon interests at first the micropylar portion and only later on the chalazal pole, that is when the ovule is about to become a seed.The role of the nucellus, endosperm and suspensor during embryo growth is discussed.