seed A seed generally develops from an ovule (PO:0020003) after fertilization, but may develop without fertilization in the case of apogamy (e.g., adventitious embryos or somatic embryos). A seed is a reproductive unit of seed plants (gymnosperms, angiosperms, and fossil pteridosperms). A multi-tissue plant structure (PO:0025496) that develops from a plant ovule (PO:0020003) and has as parts a plant embryo (PO:0009009) enclosed in a seed coat (PO:0009088). A matured ovule containing an embryo and food supply and covered by a seed coat. plant anatomical entity