11. What is triple fusion? Where and how does it take place? Name the nuclei involved in triple fusion.
A pollen grain produces two male gametes. Out of these, one male gamete fuses with the egg cell and produces a zygote. The second male gamete fuses with the two polar nuclei of the central cell to produce primary endosperm nucleus. Since this fusion includes three haploid nuclei, it is called triple fusion.
The process of triple fusion occurs in the central cell of embryo sac. The pollen tube delivers one nucleus to the egg cell while the other one migrates to centre and fuses polar nuclei.
In triple fusion, two polar nuclei and one male gamete are involved.