Double Fertilization and Triple Fusion in Plant

Double fertilization:

• S.G. Nawaschin and L.Guignard in 1898 and 1899, observed in Lilium and Fritillaria that both the male gametes released from a male gametophyte are involved in the fertilization. They fertilize two different components of the embryo sac.
• The fusion of one male gamete with an egg and that of another male gamete with two polar nuclei (secondary nucleus). Since both the male gametes are involved in fertilization, the phenomenon is called double fertilization.
• It is the characteristic feature of angiosperms.

It consists of two processes:

1. Syngamy: One of the male gametes fuses with the egg nucleus (syngamy) to form Zygote which develops to form an embryo.
2. Triple fusion: The second gamete migrates to the central cell where it fuses with the polar nuclei or their fusion product, the secondary nucleus, and forms the primary endosperm nucleus (PEN). Since this involves the fusion of three nuclei, this phenomenon is called triple fusion. This act results in endosperm formation which forms the nutritive tissue for the embryo.
   

   Fertilization in Angiosperms