During endosperm development, the embryo sac of gymnosperms differentiates from micropyle cells to archegonium. Therefore, embryo sac is a haploid gametophyte composed of endosperm and archegonium. Or the highly specialized female gametophyte in the nucellus of angiosperms is the product of megaspore mitosis. Generally, it is a "seven-cell eight nuclear" (that is, a seven-cell eight nuclear), which includes an egg cell, two auxiliary cells, a central large cell (which contains two polar nuclei) and three antipodal cells.
Basic structure The most common shape of angiosperm embryo sac is the structure of 8 nuclei and 7 cells. Besides Polygonum type, there are onion type, Five Blessingg flower type and Fritillaria type. Eggs are generally accompanied by two helper cells, with 65,438+0 helper cells in the interdigitated grass type, and helpless cells in the plumbago type and the plumbago type. Antipodocytes are ubiquitous, but their number and ploidy are variable.
The contact surface between functional embryo sac and its surrounding cells often has the structure of transmitting cells, and the cell wall protrudes inward, which is related to the transportation and absorption of nutrients. The embryo sac of some plants has haustorium.