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(1) In botany, a squamous growth on the outer side of the embryo of many herbs. The epiblast covers the plumule partially or completely. It is well expressed in most bread grains and meadow grasses, for example, rice, Poa, barley, and bamboo. It is absent in millet, sorghum, corn, and canes. The epiblast protects the plumule. During germination it swells greatly, accumulating moisture like a sponge and participating in dehiscence of the caryopsis. The morphological nature of the epiblast is unclear.

(2) In zoology, the outer epithelial layer of the discoblastula, or blastoderm, in scorpions, cephalopods, mollusks, sharks, and bony fishes, as well as in most reptiles, birds, and lower mammals. The epiblast contains ectodermal and mesodermal material. It is isolated from the cells of the internal layer, or hypoblast, by a cavity known as the blastocoel.

References in periodicals archive ?
The homeoprotein Nanog is required for maintenance of pluripotency in mouse epiblast and ES cells.
4 kb inversion in the chloroplast genome in Joinvillea and the grasses; reduction to 1 ovule per pistil, gain of a lateral "grass-type" embryo, and gain of an inversion around the gene trnT in the chloroplast genome in the grasses; loss of arm cells in the clade that consists of Brachyelytrum, Pooideae, and the PACC clade; loss of the epiblast and gain of an elongate mesocotyl internode in the PACC clade; gain of proximal female-sterile florets in female-fertile spikelets, gain of overlapping embryonic leaf margins, and gain of Panicum-type endosperm starch grains in the clade that comprises Centothecoideae and Panicoideae; and loss of the scutellar tail of the embryo in Pooideae (in one of two alternative placements of Pooideae among other groups).
embryo mesocotyl internode negligible, epiblast present, scutellar tail absent, embryonic leaf margins overlapping), a pattern typical of Oryzeae, not unknown in Pooideae, and unrecorded within the PACC clade.