Fertilisation

The fusion of the male reproductive nucleus and the female reproductive nucleus is called “Fertilization”.

• When the pollen reaches the ripened stigma of a flower, the stigma secretes a sugary substance.
• A fine tube-like structure is grown form the pollen grain called the pollen tube.
• This tube passes through the style and reach the ovule of the ovary.
• At the end of the pollen tube there are two nuclei.
  a) The tube nucleus and b) The generative nucleus.
• The generative nucleus divides forming two male nuclei while the tube nucleus disappears.
• Each ovule has two outer layers and at their upper end there is an opening called “micropyle”.
• Inside the ovule is the embryo sac and there are two nuclei inside the embryo sac.
• One of them is known as the nuclei inside the embryo sac.
• One of them is known as the Egg cell and the other as secondary nucleus.
• When the pollen tube passes through the micropyle into the ovule, the tip ofthe pollen tube breaks.
• One of the male reproductive nuclei fuses with egg cell forming a “Zygote”.
• This process is called fertilization.

Characteristics of fertilisation

• The process of formation of male gametophyte in case of plants is called as microsporogenesis.
• The process of formation of female gametophyte in case of plants is called as megasporogenesis.
• The process of pollination occurs, due to which the anthers get stuck up to the stigma.
• After reaching to stigma pollen grains develops a pollen tube.
• This pollen tube grows through the length of style, from where it reaches to ovule.
• Pollen tube comprises of two male gametes, which is later on released in the embryo sac through an opening called as micropyle.

Here one male gamete fuses with the egg to form a diploid zygote and the other male gamete fuses with the polar bodies to form a triploid nucleus which later on produces the structure called as endosperm.