Explain nuclear and helobial type of endosperm with suitable examples.

Answer: Endosperm develops from the primary endosperm nucleus (triploid, 3n) formed by triple fusion.

Nuclear endosperm: the primary endosperm nucleus divides repeatedly by free nuclear divisions without wall formation, so numerous free nuclei lie in the common cytoplasm of the central cell, usually towards the periphery with a central vacuole. Later, wall formation occurs from the periphery towards the centre and the endosperm becomes cellular; sometimes the centre remains free nuclear. Examples: coconut (the water is free-nuclear endosperm and the white kernel is cellular endosperm), maize, wheat, rice, cotton.

Helobial endosperm: the first division of the primary endosperm nucleus is followed by wall formation, dividing the central cell into a large micropylar chamber and a small chalazal chamber. Then free nuclear divisions occur in each chamber (more in the micropylar chamber), and later the endosperm may become cellular. It is intermediate between nuclear and cellular types and is common in the order Helobiales (monocots). Examples: Asphodelus, Eremurus.