Early events in higher-plant embryogenesis

The mechanisms underlying the sequence of events during plant embryogenesis have been studied in more that 600 species belonging to Di- and Monocots. In all case there are an apical cell population at the origin of the shoot apical meristem and a basal population at the origin of the root meristem. In these two populations the cell division pattern is stereotyped in some taxons, but is nevertheless variable between embryos: the orientation of cell division per se seems not to be instrumental in the establishment of the basic body plan. Cell-fate specification is position dependent; there are no cell lineage of fixed fate. The emergence of cotyledon primordia is similar to post embryonic leaf formation by the shoot apical meristem. During the development of the Monocotyledons, the differential growth in the single cotyledon results in a more or less lateral shoot apical meristem.