Flowering plants reproduce sexually through flowers. The flower contains the male parts (stamens) and female parts (carpels/pistils) that produce gametes.
Parts of a Flower
- Stamen (male): the anther produces pollen grains (male gametes), held up by the filament.
- Carpel/pistil (female): the stigma receives pollen, the style connects it to the ovary, which contains ovules (female gametes).
- Petals: brightly coloured to attract insects.
- Sepals: protect the flower in the bud stage.
Pollination
Pollination is the transfer of pollen grains from the anther to the stigma of a flower.
- Self-pollination: pollen is transferred to the stigma of the same flower or another flower on the same plant.
- Cross-pollination: pollen is transferred to a flower on a different plant of the same species.
Agents of Pollination
| Agent | Flower adaptations |
|---|---|
| Insects (e.g. bees) | Large, brightly coloured petals, scent, nectar |
| Wind | Small, dull flowers, light/dry pollen, feathery stigma, long filaments |
| Water | Light flowers that float |
Fertilisation
After pollination, a pollen tube grows down the style into the ovary. The male nucleus fuses with the female nucleus (ovum) in the ovule — this is fertilisation. The ovule develops into a seed and the ovary becomes the fruit.
Key distinction: Pollination is the transfer of pollen; fertilisation is the fusion of the male and female gametes. They are different processes that occur in sequence.
Summary
A flower’s male stamen produces pollen and the female carpel contains ovules. Pollination (by insects, wind or water) brings pollen to the stigma, after which fertilisation occurs and the ovule becomes a seed and the ovary a fruit.
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