part of seed germination seed development multicellular organismal reproductive process mucilage extrusion from seed coat The process in which seed mucilage expands through hydration and breaks the outer cell wall that encapsulates the whole seed upon imbibition. Mucilage, mainly composed of pectins, is formed during seed development and deposited into the apoplast underneath the outer wall of the seed coat. GO:0080001 biological_process secretion of mucilage from seed coat mucilage release from seed coat