IGCSE Biology / Reproduction in plants
The pollen tube and fertilisation revision notes
Edexcel International GCSE Biology (4BI1), chapter 13: Reproduction in plants, specification point 3.4. Free lesson.
Watch the video lesson · IGCSE Biology past papers
A pollen tube carries the male gamete nucleus to an ovule, where it fuses with the female gamete nucleus. After fertilisation, the zygote becomes an embryo, the ovule becomes a seed and the ovary becomes a fruit.
How the pollen tube reaches an ovule
A pollen grain must get its male gamete nucleus to an ovule, which may be some distance away. The pollen tube grows through the flower’s tissues to carry it there.
Where fertilisation happens
Inside the ovule, the male gamete nucleus fuses with the female gamete nucleus. This fusion is fertilisation, and it produces a zygote. Fertilisation happens inside the ovule, which is in the ovary. Remember the order: the pollen tube carries the male nucleus into the ovule, then the nuclei fuse.
What changes after fertilisation
After fertilisation, the zygote and parts of the flower develop into structures that support and protect the young plant. Other flower parts wither because their job is finished. The zygote divides and becomes the embryo, the young plant inside the seed. The rest of the ovule becomes a seed, with a tough coat around it. The ovary becomes the fruit, which surrounds and protects the seeds and often helps disperse them. A pea pod is a ripened ovary, and the peas inside it are seeds. The petals, sepals, stamens and stigma wither and fall off.
How pollination differs from fertilisation
Pollination and fertilisation are separate events, and they can happen days apart. A pollen grain may land on a stigma without fertilising anything. Pollination is the transfer of pollen from an anther to a stigma. Fertilisation is the fusion of the male and female gamete nuclei inside the ovule. Pollination transfers pollen. Fertilisation fuses nuclei.