A plant embryo development stage (PO:0007631) that occurs during the interval between the first cell division of a plant zygote (PO:0000423) and the onset of the plant globular embryo stage (PO:0001185). [source: APweb:Glossary, POC:Laurel_Cooper, TAIR:Katica_Ilic]
Comment
The plant proembryo stage occurs prior to the differentiation of the three main tissue systems (vascular system (PO:0000034) epidermis (PO:0005679); and the portion of ground tissue (PO:0025059)).