The endosperm development is a result of triple fusion. During triple fusion, one of the male gametes fuses with the two polar nuclei of the central cell and give rise to primary endosperm cell (PEC). The primary endosperm cell divides repeatedly and forms a triploid endosperm tissue. The most common type of endosperm development is free-nuclear, in which the PEN undergoes successive nuclear divisions to give rise to a number of free nuclei. The endosperm thus formed is called free nuclear endosperm. Subsequently, cell formation occurs and the endosperm becomes cellular.
The endosperm thus developed is required to provide essential nutrients to the growing embryo.
Therefore endosperm development occurs before the embryo development.
