Class 12th Notes On Fertilisation & Double Fertilisation

                                            Fertilization 

In Angiosperm , fertilization or syngamy  is the process of interaction  of two opposite gamete for the formation of  the zygote  which  later develops into an embryo .   After fertilization the ovule forms the seed while ovary converts into fruit .

Process -  The  pollen grain  of the flower flow through the  air or attached to the   insects and reach  to the flower . This pollen grain  starts to germinate on the stigma of the female gametophyte and the pollen tube arises to develop through the style and reach to the ovule of the embryo sac . This pollen tube contains  two cells ; generative cells and vegetative cells . The vegetative cells have a reserved food material through which generative cell mature and divides.  Later on changed into  two male gamete cells .

 Now , the pollen tube enters into the  embryo sac through the micropyle region into one of the  synergid cells by  penetrating the filiform apparatus and deliver two male gametes while the other synergid cell will disintegrate  .  One male gamete combines with the egg to form zygote  , this later on   develops into the embryo similarly  the other male gamete fuses with the polar nuclei and form a  triploid cell or  Primary Endosperm Nucleus (PEN ) .

The union of two male gametes with the different nuclei of the embryo is known as Double Fertilization which is first discovered by the Russian scientist    S. G. Nawaschin in 1898  in Lilium and fritillaria .