Question

Which of the following is the other name for secondary nucleus?
(a) Generative nucleus
(b) Tube nucleus
(c) Definitive nucleus
(d) Primary endosperm nucleus

Answer 1

Cell is developed by the combination of the sperm core and two polar cores of the central cell (or diploid auxiliary endosperm core, in this situation where two polar nuclei fuse before double fertilization). The first cell of the endosperm, often triploid.

Complete answer
The secondary nucleus is defined as when the diploid nucleus is formed by the fusion of two polar nuclei. And it is also called a primary endosperm nucleus.
The endosperm is made when the 2 sperm cores inside a pollen grain come within a female gametophyte (some of the time called the embryo sac). One sperm core fertilizes the ovum, shaping a zygote, while the contrary sperm core generally fuses with the binucleate focal cell, framing an essential endosperm cell (its core is often called the triple fusion nucleus). That cell created within the process of double fertilization develops into the endosperm. Because it's formed by separate fertilization, the endosperm constitutes an organism that breaks away from the growing embryo.
In polyploid, about $70\%$ of angiosperm species have endosperm cells. These are commonly triploid (containing three arrangements of chromosomes), yet can change generally from diploid (2n) to 15n.

So the correct answer is ‘Primary endosperm nucleus’.

Note:
One species of angiosperm, Nuphar polysepala , has been shown to possess an endosperm that's diploid, resulting from the fusion of a pollen nucleus with one, instead of two, maternal nuclei. The same is meant for a few other basal angiosperms. It's accepted that ahead of schedule inside the advancement of angiosperm ancestries, there was a duplication during this method of proliferation, making seven-celled/eight-nucleate female gametophytes, and triploid endosperms with a 2:1 maternal to fatherly genome proportion.