Lesson focus: After compatible pollen germinates, a pollen tubeA tiny tube that grows from a pollen grain down to the ovule, carrying the male sex cell. delivers male gamete nuclei to an ovule, where fertilisationWhen the nucleus of a male sex cell (gamete) fuses with the nucleus of a female sex cell to form a zygote. initiates seedThe part of a plant that contains a baby plant (embryo) and a food store. development.
Sequence pollen-tube growth, fertilisation, seed and fruit formation, then distinguish germinationWhen a seed starts to grow into a new plant. from fertilisation.
Build on earlier learning
Flowers and pollinationPollination placed pollen on a compatible stigma. This lesson follows the cellular events that can occur afterward.
You will be successful when you can…
- Sequence events after pollination.
- Define fertilisation as fusion of nuclei.
- Relate ovule to seed and ovary to fruit.
- State the conditions and purpose of germination.
Words that carry the science
- pollen tube
- A tube grown by a pollen grain that carries male gamete nuclei toward an ovule.
- fertilisation
- Fusion of male and female gamete nuclei.
- zygote
- The diploid cell formed by fertilisation.
- embryo
- The young developing plant within a seed.
- seed
- A mature ovule containing an embryo, food reserve and protective coat.
- germination
- Resumption of embryo growth from a seed under suitable conditions.
Trace nuclei from pollen grain to new embryo
01Compatible pollen germinates on the stigma
A pollen grain absorbs water and germinates on a compatible stigma. It grows a pollen tubeA tiny tube that grows from a pollen grain down to the ovule, carrying the male sex cell. through the style, guided toward an ovule. Male gamete nuclei move within the tube.
Compatibility mechanisms reduce unsuccessful or inappropriate fertilisationWhen the nucleus of a male sex cell (gamete) fuses with the nucleus of a female sex cell to form a zygote.. Pollen transfer alone does not guarantee tube growth or seedThe part of a plant that contains a baby plant (embryo) and a food store. production.
02Fertilisation initiates development
A male gamete nucleus fuses with the egg-cell nucleus in the ovule, forming a zygoteThe first cell of a new living thing, made when two sex cells join at fertilisation.. The zygoteThe first cell of a new living thing, made when two sex cells join at fertilisation. divides and develops into an embryoThe tiny young plant inside a seed.. In flowering plants, another male nucleus also contributes to endosperm formation through double fertilisation, an IGCSE bridge idea.
The ovule develops into a seed. The ovary commonly develops into a fruit, while petals and other structures may wither or change.
03Germination begins later
A mature seed can remain dormant. With suitable water, oxygen and temperature, metabolism increases, stored food is mobilised and the embryo resumes growth.
The radicle usually emerges before the shoot. Light is not a universal requirement for all seed germinationWhen a seed starts to grow into a new plant., although seedlings soon need light for sustained photosynthesis.
Life cycle of a flowering plant
A flowering plant grows from a seed, flowers, is pollinated and makes new seeds. Step through each stage.
Step 1 of 5
Correct a mixed-up sequence
A sequence says: seed → pollination → fruit → fertilisation → pollen tubeA tiny tube that grows from a pollen grain down to the ovule, carrying the male sex cell..
- Begin with pollination: pollen reaches a compatible stigma.
- The pollen grain germinates and grows a pollen tube.
- Male and female gamete nuclei fuse in fertilisation.
- The ovule develops into a seed and the ovary develops into a fruit.
How to make the reasoning visible: Germination occurs later when the mature seed resumes growth under suitable conditions.
Build the reproductive timeline
Link each event to its location and immediate consequence.
| Order | Event | Location | Immediate consequence |
|---|---|---|---|
| 1 | Pollination | Stigma | Compatible pollen arrives |
| 2 | Pollen germination | Stigma/style | Pollen tube begins growth |
| 3 | Fertilisation | Ovule | Gamete nuclei fuse to form zygote |
| 4 | Embryo development | Developing seed | Zygote divides and differentiates |
| 5 | Fruit/seed maturation | Ovary and ovule | Dispersal unit develops |
| 6 | Germination | Seed in suitable environment | Embryo growth resumes |
Why can pollination occur without seed formation?
Distinguish the fates of ovule and ovary.
Check your understanding
Answer from memory, then check against the suggested answer.
What is fertilisation?
What does an ovule become?
What three broad conditions do most seeds require to germinate?
A flower is pollinated but later produces no mature seeds. Give two plausible biological explanations.
Explain why endosperm formation is biologically linked to fertilisation in flowering plants.
Exam Question Practice
Exam Question Practice
Mark points shown after marking
A flowering plant reproduces sexually.
Describe pollination and fertilisation.
(3)Describe what happens after fertilisation, up to germination.
(3)Total for this question: 6 marks
Command word: For describeA command word: say what happens or what something is like, step by step, without needing to give reasons., preserve chronological order and keep pollination, fertilisation and germination distinct.