Test: Double Fertilisation - NEET MCQ

• The fusion of one male gamete with the egg cell is called Syngamy or true fertilization while the fusion of second male gamete with two polar nuclei is called triple fusion.
• Syngamy along with the triple fusion is called double fertilization. Double fertilization is a characteristic feature of flowering plants or angiosperms.   

Hence, the correct option is B.
Topic in NCERT: DOUBLE FERTILISATION
Line in NCERT: "One of the male gametes moves towards the egg cell and fuses with its nucleus thus completing the syngamy."

Double fertilisation is a unique process in angiosperms where two distinct fusion events occur. One male gamete fuses with the egg cell to form the zygote (syngamy), while the other male gamete fuses with the two polar nuclei located in the central cell, resulting in triple fusion. After triple fusion, the central cell is no longer called the central cell; it becomes the primary endosperm cell (PEC). The nucleus formed by the fusion of the three nuclei is called the primary endosperm nucleus (PEN), but the question specifically asks for the name of the cell after triple fusion, not the nucleus. Therefore, the correct answer is d) Primary endosperm cell (PEC). Reference from NCERT: "The central cell after triple fusion becomes the primary endosperm cell (PEC) and develops into the endosperm while the zygote develops into an embryo."
Topic in NCERT: POST-FERTILISATION: STRUCTURES AND EVENTS
Line in NCERT: "The central cell after triple fusion becomes the primary endosperm cell (PEC) and develops into the endosperm while the zygote develops into an embryo."

Here's the explanation in detail:
-  A are degenerating synergids, which are haploid (n) 
- B is diploid (2n) as it represents the zygote formed by the fusion of male and female gametes.
- C  is triploid (3n) as it represents endosperm formed by the fusion of two polar nuclei and a sperm cell.
- D are degenerating antipodal cells, which are haploid (n) 
This analysis validates both Statement I and Statement II ARE INCORRECT
Diagram from NCERT: 

Topic in NCERT: POST-FERTILISATION: STRUCTURES AND EVENTS
Line in NCERT: "The large central cell, as mentioned earlier, has two polar nuclei." "The zygote develops into an embryo." "Degenerating synergids" "Degenerating antipodal cells"

• The pollen grains germinate on the stigma and the resulting pollen tubes grow through the tissues of stigma and style and reach the ovule.
• The pollen tubes enter the embryo-sac where two male gametes are discharged. One of the male gametes fuses with the egg cell (syngamy) and forms a diploid zygote. The other male gamete fuses with the diploid secondary nucleus to four primary endosperm nucleus (PEN), which is triploid in nature.
• Since, two types of fusion. Syngamy and triple fusion takes place in the embryo sac, the process is known as double fertilisation. 

Topic in NCERT: DOUBLE FERTILISATION
Line in NCERT: "One of the male gametes moves towards the egg cell and fuses with its nucleus thus completing the syngamy. 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)."

In double fertilisation, after the pollen tube enters the synergid, the two male gametes are released. One fuses with the egg cell to form the diploid zygote, and the other fuses with the two polar nuclei to form the triploid primary endosperm nucleus (PEN). The zygote develops into the embryo, and the primary endosperm nucleus forms the endosperm. This process is termed double fertilisation, which is unique to flowering plants.

Topic in NCERT: DOUBLE FERTILISATION

Line in NCERT: "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)."