antipodalen

Antipodalen refers to antipodal cells, a group of cells in the embryo sac of most angiosperms. They occupy the chalazal end of the mature female gametophyte and, together with the egg apparatus and central cell, form the eight-nucleate, seven-celled structure that develops after megagametogenesis. Typically three antipodal cells are present, though their number or persistence can vary among taxa.

Development and structure: Antipodal cells arise during megagametogenesis and reside at the opposite end of the embryo sac from the egg cell. They usually contain large vacuoles and relatively little cytoplasm compared with the egg cell and synergids. In many species they degenerate before fertilization, whereas in some basal angiosperms and certain lineages the antipodals persist longer.

Function and significance: The precise function of antipodal cells is not definitively known. Many species show rapid degeneration of antipodals after the initial stages of fertilization, suggesting a limited direct role. Hypotheses include transient storage of nutrients for the embryo sac, contributions to nourishing the central cell or synergids during development, or involvement in signaling processes. In taxa where antipodals persist, they may play a more evident role in embryo sac dynamics or early seed development.

Variation: The presence and longevity of antipodal cells vary across angiosperms. While three antipodal cells are common, some species exhibit different numbers or patterns of degeneration. Antipodals are a standard feature of the mature embryo sac in many flowering plants, but their exact contribution remains an area of study.

See also: Embryo sac, megagametogenesis, polar nuclei, synergids, egg cell.