Triple fusion is a process that occurs during the sexual reproduction of flowering plants, where three haploid nuclei from two different cells fuse to form a triploid nucleus. It is also known as the fusion of the male and female gametes with the fusion of a second male nucleus.
In flowering plants, the triple fusion takes place in the embryo sac, which is located within the ovule of the flower's female reproductive organ (pistil). The two male nuclei are present within the pollen grain, which is produced by the male reproductive organ (stamen) and transported by wind or insects to the stigma of the pistil.
Once the pollen grain lands on the stigma, it germinates and produces a tube that grows down the style and enters the ovule. This tube then releases the two male nuclei into the embryo sac. One of the nuclei fuses with the egg cell, forming a zygote, which will develop into the embryo. The other male nucleus fuses with two polar nuclei, which are located at the center of the embryo sac, forming a triploid nucleus. This process is called triple fusion.
The nuclei involved in triple fusion are the haploid nucleus of the male gamete, the haploid nucleus of the female gamete (egg cell), and the haploid nucleus of the central cell (formed by the fusion of two polar nuclei) within the embryo sac.