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

In no case was any trace of embryo sac to be seen.

From Project Gutenberg

In the full-grown ovule the macrospore, which in the seed plants is generally known as the “embryo sac,” is completely filled with the prothallium or “endosperm.”

From Project Gutenberg

The structure of the embryo sac and ovules is quite constant among the angiosperms, the differences being mainly in the shape of the ovules, and the degree to which its coverings or integuments are developed.

From Project Gutenberg

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

From Project Gutenberg

The integuments grow with the embryo sac, and become brown and hard, forming the shell of the seed.

From Project Gutenberg