The carpels are in the centre of the flower. They are made up of three parts:
1. The stigma acts as a landing area for pollen. 2. The style is a stalk that positions the stigma for pollen collection.
3. The ovary contains ovules, which produce the female gamete (egg). It is also where fertilisation takes place. After fertilisation, the ovary develops into the fruit.
z z z z
The sepals protect the flower as a bud. The petals attract insects for pollination.
The Stages of Sexual Reproduction in Flowering Plants There are five stages in the sexual reproduction of a plant: 1. Pollination 2. Fertilisation 3. Seed (and fruit) formation 4. Seed (and fruit) dispersal 5. Germination
1. Pollination
For fertilisation to take place, the male gamete in the pollen must get to the female gamete in the ovary. The transfer of pollen from the anther to the stigma is called pollination. Pollination can be carried out by the wind, by insects or by other animals.
Pollen caught by stigma
Anther Nectary
Anthers hang outside flower
z
Fig. 7.4.3 Wind pollination
2. Fertilisation
1. If a pollen grain of the same species lands on the stigma, a pollen tube grows.
2. The pollen tube delivers the male sperm to the female egg in the ovule of the ovary.
3. The sperm and egg fuse to form a zygote. 121 Pollen blown by wind z Fig. 7.4.4 Insect pollination z Fig. 7.4.2
Hay fever is caused by pollen in the air
F Lots of
people suffer from hay fever caused by a reaction to pollen. When do you think hay fever is at its peak? Why?
