What is triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion.
Triple fusion is the fusion of three haploid nuclei to produce a triploid primary endosperm nucleus (PEN). This involves the fusion of one male gamete with two polar nuclei.
Triple fusion takes place in the central cell of the embryo sac. After entering one of the synergids, the pollen tube releases two male gametes. One 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). The central cell after triple fusion becomes the primary endosperm cell (PEC).
The nuclei involved in triple fusion are:
- One male gamete nucleus (haploid)
- Two polar nuclei (haploid) from the central cell
Explanation
This question tests understanding of double fertilization in flowering plants, specifically the triple fusion event. The textbook explains that after entering the synergid, the pollen tube releases two male gametes. While one fuses with the egg cell (syngamy), the other moves toward the two polar nuclei in the central cell. The fusion of these three haploid nuclei (one male gamete + two polar nuclei) is called triple fusion, resulting in a triploid primary endosperm nucleus. This is a unique feature of angiosperms.