Learning objectives
- Label a flower and state each function
- Compare wind- and insect-pollinated flowers
- Describe fertilisation and the fate of flower parts after it
1. Parts of the flower
Sepals protect the bud; petals attract pollinators; the stamen (anther and filament) produces pollen; the carpel or pistil (stigma, style, ovary) receives pollen and contains the ovules; the receptacle supports the whole flower.
2. Pollination
Pollination is the transfer of pollen from anther to stigma. Self-pollination occurs within the same flower or plant and preserves parental characters; cross-pollination transfers pollen between different plants of the same species and increases genetic variation.
- Insect-pollinated — large bright petals, scent, nectar, sticky pollen, enclosed anthers and stigma
- Wind-pollinated — small dull petals or none, no scent or nectar, light smooth pollen, exposed feathery stigma and pendulous anthers
3. Fertilisation and after
The pollen grain germinates on the stigma and grows a pollen tube down the style to the ovule, where the male nucleus fuses with the egg cell. In angiosperms, double fertilisation also forms the triploid endosperm.
After fertilisation the ovule becomes the seed, the ovary becomes the fruit, and the petals, stamens and stigma wither and fall.
4. Seed dispersal
Dispersal reduces competition between parent and offspring. Learn one example each of dispersal by wind (winged or plumed seeds), water (buoyant fibrous coats), animals (hooks or edible fruits) and explosive mechanisms (pods that split).
Key definitions
- Pollination
- Transfer of pollen grains from the anther to the stigma of a flower.
- Double fertilisation
- Fusion of one male nucleus with the egg and another with the polar nuclei to form endosperm.
- Dispersal
- Movement of seeds away from the parent plant to reduce competition.
Exam tips
- In comparison questions always write both sides of the comparison in the same sentence.
- Pollination is not fertilisation — define the difference clearly if both appear in a question.
Practice exam questions & model answers
Q1.Give four adaptations of a wind-pollinated flower.
Small, dull or absent petals; no nectar or scent; large quantities of light, smooth pollen; anthers hanging outside the flower and large feathery stigmas exposed to catch airborne pollen.
Q2.State two advantages of cross-pollination.
It increases genetic variation, producing offspring better able to adapt and resist disease, and it generally yields more vigorous seedlings (hybrid vigour).
Q3.What happens to the ovary and ovule after fertilisation?
The ovule develops into the seed and the ovary develops into the fruit.
Continue revising
Plant Cell Structure and Function
Plant BiologyPhotosynthesis: Process, Equation and Limiting Factors
BotanyLeaf Structure, Stomata and Transpiration
Agricultural SciencePlant Nutrition, NPK and Soil Fertility
Put the theory to work — diagnose a real leaf photo or browse the disease library.