root radicle May develop into the primary root (PO:0020127) and eventually the root system (PO:0025025) of an adult plant. Sometimes abortive. The lower part of the axis of a plant embryo or seedling. An embryo root (PO:0000045) that is the basal continuation of a hypocotyl (PO:0020100) in a plant embryo (PO:0009009) or a seedling (PO:0000003).