proembryo

The term "proembryo" refers to the early stage of embryo development in plants. Following fertilization, the zygote undergoes cell division to form the initial cells of the embryo sporophyte. This stage is characterized by the development of primary organs like the first root, first leaves, and the shoot apex. Temporary structures such as the suspensor and foot may also form to aid in embryo nutrition.1

In angiosperms (flowering plants), embryogenesis begins with the zygote dividing into two cells: the terminal cell and the basal cell. The terminal cell develops into the seed leaves (cotyledons) and the shoot apex, while the basal cell forms the hypocotyl and contributes to the root. The suspensor, formed from the basal cell, pushes the developing embryo into the gametophyte or endosperm for nourishment.2

The embryo's early growth is dependent on either the gametophyte or, in angiosperms, the endosperm, which is a nutritive tissue derived from the parent sporophyte. The proembryo stage is crucial for establishing the basic body plan of the future plant.32