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How do flowering plants reproduce by pollination and fertilisation?

Describe sexual reproduction in flowering plants including pollination and fertilisation

A focused answer to the O-Level Biology outcome on plant reproduction. The parts of a flower, the difference between insect and wind pollination, and the steps of pollination and fertilisation.

Generated by Claude Opus 4.88 min answer

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  1. What this dot point is asking
  2. The answer
  3. Examples in context
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What this dot point is asking

SEAB wants you to describe sexual reproduction in flowering plants: the parts of a flower and their functions, the difference between pollination and fertilisation, how insect-pollinated and wind-pollinated flowers differ, and the steps from a pollen grain landing on a stigma to the formation of a seed.

The answer

The parts of a flower

A flower contains the male and female reproductive parts:

  • The stamen is the male part: an anther (which makes pollen) held up by a filament.
  • The carpel is the female part: a stigma (which receives pollen), a style, and an ovary containing ovules (which contain the female gametes).
  • Petals attract pollinators (in insect-pollinated flowers); sepals protect the bud.

The pollen contains the male gametes; the ovule contains the female gamete (the egg cell).

Pollination

Pollination is the transfer of pollen from the anther of a stamen to the stigma of a carpel. It can happen within one flower (self-pollination) or between flowers of the same kind (cross-pollination). Pollen is carried either by insects or by the wind.

Insect-pollinated versus wind-pollinated flowers

The flowers are adapted to their method:

  • Insect-pollinated flowers have large, brightly coloured, scented petals with nectar to attract insects; their anthers and stigmas are inside the flower so the insect brushes against them; their pollen is sticky or spiky to cling to the insect.
  • Wind-pollinated flowers have small, dull or no petals and no scent; their anthers hang outside so the wind blows the pollen away; their stigmas are large and feathery, hanging out to catch pollen from the air; their pollen is light and produced in large amounts.

Fertilisation

After a pollen grain lands on the stigma, it grows a pollen tube down through the style to the ovary, guided to an ovule. The male gamete nucleus travels down the tube and fuses with the female gamete nucleus (the egg cell) inside the ovule. This fusion is fertilisation, forming a zygote.

After fertilisation, the ovule becomes a seed (containing the embryo) and the ovary becomes a fruit.

Examples in context

Example 1. A bee on a flower. A bee visiting a bright, scented flower for nectar brushes against the anthers, picking up sticky pollen. At the next flower it brushes the stigma, transferring the pollen, an example of insect pollination.

Example 2. Grass pollen and hay fever. Grasses are wind-pollinated and release huge amounts of light pollen into the air. Much of it never reaches a stigma, but some triggers hay fever in people, showing why wind-pollinated plants make so much pollen.

Try this

Q1. Define pollination. [2 marks]

  • Cue. The transfer of pollen from the anther of a stamen to the stigma of a carpel.

Q2. State one feature of a wind-pollinated flower and its purpose. [2 marks]

  • Cue. A large feathery stigma (hanging outside) to catch pollen carried in the air; or anthers that hang outside so wind blows the pollen away.

Q3. State what the ovule and the ovary become after fertilisation. [2 marks]

  • Cue. The ovule becomes a seed and the ovary becomes a fruit.

Exam-style practice questions

Practice questions written in the style of SEAB exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.

Original6 marks(a) Define pollination. (b) Compare an insect-pollinated flower and a wind-pollinated flower by giving one difference in their petals, one in their stamens, and one in their stigmas.
Show worked answer →

(a) Pollination is the transfer of pollen from the anther (of a stamen) to the stigma (of a carpel) of a flower.

(b) Petals: insect-pollinated flowers have large, brightly coloured, scented petals (with nectar) to attract insects; wind-pollinated flowers have small, dull or no petals. Stamens: in insect-pollinated flowers the anthers are inside the flower so insects brush against them; in wind-pollinated flowers the anthers hang outside so the wind can blow the pollen away. Stigmas: insect-pollinated stigmas are small and inside the flower; wind-pollinated stigmas are large and feathery, hanging out to catch pollen from the air.

Markers reward a correct definition of pollination and a correct contrast for each of the three named parts, matched to attracting insects or catching the wind.

Original4 marksAfter a pollen grain lands on the stigma, describe how fertilisation takes place in a flowering plant.
Show worked answer →

The pollen grain grows a pollen tube down through the style toward the ovary, guided to an ovule. The male gamete (the nucleus in the pollen) travels down the pollen tube. At the ovule, the male gamete nucleus fuses with the female gamete nucleus (the egg cell) inside the ovule. This fusion is fertilisation, forming a zygote.

After fertilisation, the ovule develops into a seed and the ovary develops into a fruit.

Markers reward the pollen tube growing down the style to the ovule, the male gamete travelling down it, and the fusion of the male and female nuclei (fertilisation) at the ovule.

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