Pollination and Fertilization in Plants

Process in which pollen grains are transferred from the ripe anther to the stigma. It is of two types: 

1.0Self-Pollination

It is the transfer of pollen grains from an anther to the stigma of the same plant. If it is in the same flower, it is called autogamy (e.g. Pea) and if it is between flowers of the same plant then it is called geitonogamy (e.g. Oxalis).

2.0Cross Pollination

It is the transfer of pollen grains from anther to the stigma of different plants of the same species, it is also called xenogamy.

When the male and female reproductive parts are present in the same flower, it is called a bisexual flower e.g. Hibiscus, Mustard, Pea. When the male and female reproductive parts are present in different flowers, they are called unisexual flowers e.g. papaya, date palm, mulberry, gourd, water melon.

3.0Agencies of Pollination

Transfer of pollen from one flower to another is achieved by agents like wind, water or animals.

4.0Fertilization in Plants

Fertilization is the process of fusion of the male and female gametes to form a zygote which takes place in the embryo sac present in the ovule.

After pollination, pollen grains germinate on the stigma by producing pollen tube.  It then penetrates the stigma and passes through the style. The nucleus in the pollen tube divides into two male gametes/germ cells. Pollen tube enters the ovule through a narrow pore called micropyle. It releases two male gametes in the embryo sac. 

One male gamete fuses with an egg cell and the second male gamete fuses with the two polar nuclei.

A fully developed typical angiospermic embryo sac consists of seven cells and eight nucleus stages. 3 antipodal cells, 2 synergids, a central cell containing 2 polar nuclei (which fuse to form a secondary nucleus) and 1 egg cell.

5.0Differences Between Pollination and Fertilization