The joining of 2 or more lipid bilayer membranes that surround the nucleus.

The process whose specific outcome is the progression of the embryo sac over time, from its formation to the mature structure. The process begins with the meiosis of the megasporocyte to form four haploid megaspores. Three of the megaspores disintegrate, and the fourth undergoes mitosis giving rise to a binucleate syncytial embryo sac. The two haploid nuclei migrate to the opposite poles of the embryo sac and then undergo two rounds of mitosis generating four haploid nuclei at each pole. One nucleus from each set of four migrates to the center of the cell. Cellularization occurs, resulting in an eight-nucleate seven-celled structure. This structure contains two synergid cells and an egg cell at the micropylar end, and three antipodal cells at the other end. A binucleate endosperm mother cell is formed at the center. The two polar nuclei fuse resulting in a mononucleate diploid endosperm mother cell. The three antipodal cells degenerate.

The process in which the eight-nucleate single celled female gametophyte develops into the seven-celled female gametophyte. This mature structure contains two synergid cells and an egg cell at the micropylar end, and three antipodal cells at the other end. A binucleate endosperm mother cell is formed at the center. An example of this process is found in Arabidopsis thaliana.

The merging of the polar nuclei, the two nuclei contained within the same cell that are created from the mitotic division of the megaspore during angiosperm reproduction. Polar nuclear fusion takes place in the ovule, forming in the fusion nucleus and giving rise to the endosperm when fertilized.

Synergid cells undergo degeneration and death in response to penetration by the pollen tube. It is an active process that involves a dramatic decrease in cell volume, collapse of the vacuoles, and complete disintegration of the plasma membrane and most organelles.

The process of assisting in the correct posttranslational noncovalent assembly of proteins, which is dependent on additional protein cofactors. This process occurs over one or several cycles of nucleotide hydrolysis-dependent binding and release.

A semiautonomous, self replicating organelle that occurs in varying numbers, shapes, and sizes in the cytoplasm of virtually all eukaryotic cells. It is notably the site of tissue respiration.