Explain sexual reproduction in angiosperms

 

Hi Chikitha,

Sexual reproduction in angiosperms occurs with the help of flowers. Flower is the reproductive organ in angiosperms.

The male organ of the flower is called stamen. It makes male gametes (pollen grains). The female organ of the flower is called carpel. It makes female gametes. These gametes present in ovules are called ova or egg.

Reproduction in angiosperms occurs in a stepwise manner and includes processes like pollination, fertilisation and fruit and seed formation.

Pollination:
The transfer of pollen grains from anther of stamen to stigma of carpel is called pollination. It is done by insects, birds, wind and water.

Fertilisation:

• When pollen grain falls on the stigma of carpel, it bursts open and grows into a pollen tube downwards through the style towards female gamete in ovary.
• A male gamete moves down the pollen tube. The pollen tube enters the ovule in ovary. The tip of pollen tube bursts open and male gamete comes out of pollen tube. In ovary, male gamete of pollen combines with nucleus of female gamete or egg present in ovule to form a fertilised egg called zygote.

Formation of Fruit and Seeds:

• The zygote divides several times to form an embryo within the ovule.
• The ovule develops a tough coat around it and gradually gets converted into a seed.
• The ovary grows rapidly and ripens to form a fruit (with seed inside it).
• The other part of the flower like sepals, petals, stamen, stigma, style dry up and fall off.