question_answer

Directions : (56 - 60)

Read the passage given below and answer the following questions.

In angiosperm, the male gametes are brought to the egg containing embryo sac by a pollen tube. The phenomenon is called siphonogamy. After entering one of the synergids, the pollen tube releases the two haploid non motile 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 or oospore it further develops into an embryo. False fertilization: The other male gamete moves towards the two haploid polar nuclei or diploid secondary nucleus located in the central cell and fuses with them to produce a triploid primary endosperm nucleus (PEN). As this involves the fusion of three haploid nuclei it is termed triple fusion. The central cell after triple fusion becomes the primary endosperm cell (PEC) and develops into the endosperm (3n). Since two types of fusions, syngamy and triple fusion take place in an embryo sac the phenomenon is termed double fertilisation, an event unique to flowering plants.

Triple fusion involves fusion of :

A) Two male gametes and one egg

B) Two male gametes and secondary nucleus

C) Two eggs and one male gamete

D) One male gamete and two polar nuclei