Questions & Answers

In a nuclear endosperm, which of the following is seen?
(a)Every nuclear division is followed by wall formation
(b)Initially, free-nuclear division followed by wall formation
(c)First division followed by wall formation and other free nuclear
(d)None of the above

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Hint:The nuclear endosperm is also known as liquid endosperm as seen in coconut. In coconut, the peripheral endosperm is usually multicellular which is called ‘coconut meal’ while the central part called ‘coconut milk’ is free nuclear.

Complete answer:
The nuclear endosperm is formed by continuous mitotic free nuclear division of the PEN (primary endosperm nucleus) in the central cell of the embryo. Later, the formation of the wall takes place in centrifugal direction i.e. from the periphery of the embryo sac to the center. This is preceded by the formation of a large central vacuole that pushes the free nuclei to the peripheral cytoplasm.
It is the commonest kind of endosperm and is found mainly in polypetalous flowers such as cotton, wheat, sunflower, Zea mays, Capsella, Coconut, etc.

Additional information:
The other two types of endosperm are-
-Cellular endosperm- In this type of endosperm, the nuclear divisions are followed by immediate wall formation. It is seen in Petunia, Datura, Adoxa, etc.
-Helobial endosperm- It is an intermediate type of endosperm in which the first nuclear division is followed by wall formation but the subsequent nuclear divisions take place without any wall formation. It is seen in monocots like Asphodelus.

So, the correct answer is ‘Initially free-nuclear division followed by wall formation’.

Note:
-The endosperm acts as a source of nutrition to the developing seed and consists of starch (mainly), protein, and fatty oils.
-The endosperm of the majority of the angiosperms is triploid except for a few such as, in Nuphor polsepala, the endosperm is diploid.