embryo sac

American  

noun

Botany.

1. the megaspore of a seed-bearing plant, situated within the ovule, giving rise to the endosperm and forming the egg cell or nucleus from which the embryo plant develops after fertilization.

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embryo sac British  

noun

1. the structure within a plant ovule that contains the egg cell: develops from the megaspore and contains the embryo plant and endosperm after fertilization

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embryo sac Scientific  

1. An oval structure within an ovule of an angiosperm that contains the egg. Together with the fertilized egg, it develops into a seed. The embryo sac is the female gametophyte of angiosperms, consisting of eight nuclei: the egg and two adjacent and short-lived synergids that are near the micropyle (the opening where the pollen nuclei will enter), two central nuclei (which will combine with one of the pollen nuclei to form the endosperm), and three antipodal nuclei at the end of the embryo sac opposite the micropyle. Like the synergids, these nuclei degenerate at or shortly after fertilization.

2. See more at gametophyte pollination

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Etymology

Origin of embryo sac

First recorded in 1870–75

Example Sentences

A double-layered integument protects the megasporangium and, later, the embryo sac.

From Textbooks • Jan. 1, 2015

Illustration depicts the embryo sac of an angiosperm, which is egg-shaped.

From Textbooks • Jan. 1, 2015

Two polar nuclei are inside the central cell in the middle of the embryo sac.

From Textbooks • Jan. 1, 2015

The other sperm fuses with the diploid nucleus in the center of the embryo sac, forming a triploid cell that will develop into the endosperm: a tissue that serves as a food reserve.

From Textbooks • Apr. 25, 2013

It is a small, pear-shaped mass of cells, the smaller end directed toward the upper end of the embryo sac.

From Elements of Structural and Systematic Botany For High Schools and Elementary College Courses by Campbell, Douglas Houghton