Which of the following structures is formed after the fusion of one o…

The correct answer is Option (3) → Primary endosperm nucleus

Flowering plants show double fertilisation. The pollen tube releases two male gametes into a synergid. One male gamete fuses with the egg (syngamy). The other fuses with the two polar nuclei of the central cell. This second fusion joins three haploid nuclei, so it is called triple fusion, and its product is triploid.

Option (1) Zygote — Incorrect. The zygote is the diploid cell formed when a male gamete fuses with the egg cell (syngamy), not with the polar nuclei.

Option (2) Scutellum — Incorrect. The scutellum is the single cotyledon of the grass embryo. It is a part of the embryo that develops later from the zygote, not the direct product of a fusion.

Option (3) Primary endosperm nucleus — Correct. The fusion of one male gamete with the two polar nuclei gives the triploid primary endosperm nucleus (PEN). The central cell then becomes the primary endosperm cell, which develops into the endosperm that feeds the growing embryo.

Option (4) Embryo — Incorrect. The embryo develops from the zygote, after the endosperm has started to form. It does not come from the polar nuclei.

NCERT Extract:
Double Fertilisation – “After entering one of the synergids, the pollen tube releases the two male gametes into the cytoplasm of the synergid. One of the male gametes moves towards the egg cell and fuses with its nucleus thus completing the syngamy. This results in the formation of a diploid cell, the zygote. The other male gamete moves towards the two polar nuclei located in the central cell and fuses with them to produce a triploid primary endosperm nucleus (PEN) (Figure 1.13a). As this involves the fusion of three haploid nuclei it is termed triple fusion.”