Ekdoderme

Ekdoderme refers to a developmental layer found in certain plant embryos, particularly in the context of early embryogenesis in angiosperms (flowering plants). The term originates from Greek, where "ekdo" means "outside" and "derme" means "skin," reflecting its position as an outer cell layer during early embryonic stages.

During the early stages of seed development, the fertilized egg cell undergoes asymmetric division, producing a larger basal cell and a smaller apical cell. The apical cell further divides to form the **proembryo**, which eventually develops into the mature embryo. In some species, particularly those with a specific type of embryogenesis known as the **monocotyledonous or dicotyledonous pattern**, an additional layer called the ekdoderme may emerge between the outer integument (seed coat) and the embryo proper. This layer is transient and typically degenerates as the embryo matures.

The ekdoderme is most prominently studied in certain monocots, such as members of the family Poaceae (grasses), where it plays a role in nutrient transfer or structural support during early embryogenesis. Its presence varies among plant species, and not all embryos exhibit this layer. Research into the ekdoderme helps elucidate the complexities of seed development and the evolutionary adaptations of plant embryos.

While the ekdoderme is not as widely discussed as other embryonic tissues like the suspensor or the hypocotyl, its study contributes to understanding the diversity of plant reproductive strategies. Further research may reveal additional functions or variations in its occurrence across different plant lineages.