Q.In angiosperms, endosperm is formed by/due to ..........

The endosperm, the nutritive tissue formed from the triploid primary endosperm nucleus (PEN) after triple fusion in angiosperms, can develop in different ways depending on the species:

Nuclear type of endosperm: In this most common type, the primary endosperm nucleus undergoes repeated free (karyokinetic) nuclear divisions without any accompanying cytokinesis (cell wall formation), so that numerous free nuclei accumulate scattered within the common cytoplasm of the enlarging endosperm sac; cell wall formation, if it occurs at all, is delayed until a later stage, typically starting at the periphery and proceeding inward (centripetally). A well-known example is the coconut, where the liquid 'coconut water' represents this free-nuclear (uncellularized) stage of nuclear endosperm, while the solid white 'coconut meat' represents the later cellularized layer.

Helobial type of endosperm: This type is intermediate in character between the nuclear and cellular types. Here, the first division of the primary endosperm nucleus is immediately followed by the formation of a cell wall (a transverse septum), which divides the developing endosperm into two chambers of unequal size right from the start — a larger micropylar chamber (near the micropylar end of the embryo sac) and a smaller chalazal chamber (near the chalazal end). The micropylar chamber typically undergoes further nuclear divisions, at first free-nuclear and later cellularized, while the chalazal chamber usually remains smaller and may not divide further, or divides only to a limited extent. This pattern is characteristically seen in members of the order Helobiales (e.g., Alisma, Butomus), from which the type derives its name. …