The embryo sac gets its nutrition from the chalazal end, nucellar or integumentary tissues. The chalazal end is recognized as the main path through which the nutrition enters the embryo sac. Between the chalazal end of the embryo sac and the vascular supply of the ovule there lies a group of specialized tissue known as the hypostase. The mode of nutrition of the embryo sac changes after fertilization. That is before fertilization the antipodals supply nutrition to the central cell, synergids and to the egg, whereas after fertilization the antipodals and the synergids degenerates so that the function of nutrition is attained from the chalazal and the micropylar endosperm haustoria. The presence of close deposits in the cell wall of the funicle, hypostase, nucellus and integumentary tapetum restricts nutrition to the ovule. This callose deposition serves as molecular filter which will blocks the flow of nutrition to the embryo sac.
