In angiosperms, pollen grain germinates to produce two male gametes. Which one of the following functions is carried out by these gametes ?

In angiosperms, the fertilization process is unique and is known as Double Fertilization. When a pollen grain germinates, it produces two male gametes that travel down the pollen tube to the embryo sac.

• First Gamete: Fuses with the haploid egg cell to form a diploid zygote (Syngamy), which eventually develops into the embryo.
• Second Gamete: Fuses with the diploid secondary nucleus (formed by the fusion of two polar nuclei) to form a triploid Primary Endosperm Nucleus (Triple Fusion).

This triploid nucleus develops into the endosperm, which provides essential nutrition to the growing embryo. Therefore, Option D is correct as it accurately describes these two distinct fusion events that characterize reproduction in flowering plants.