After fertilisation, the fertilised ovule becomes the seed and the ovary becomes the fruit. The embryo inside the seed is the new plant in miniature. This appears in diagram questions, in “what happens after fertilisation” questions and in seed dispersal explanations.
It follows directly from pollination and fertilisation.
What does each part become?
Trace every part of the flower after fertilisation.
| Before | After fertilisation |
|---|---|
| Zygote | Embryo (inside the seed) |
| Ovule | Seed |
| Ovary wall | Fruit wall |
| Petals, stamens | Wither and fall away |
The stigma and style also wither, because the pollen tube has already done its job. The plant puts its resources into the seeds.
What is inside a seed?
A seed holds everything the embryo needs to start growing.
- Testa: the tough outer coat that protects the seed.
- Embryo: a plumule (becomes the shoot) and a radicle (becomes the root).
- Cotyledons: seed leaves that store food. The food supports the seedling until it can make its own by photosynthesis.
The food store is important, because a seedling below the soil has no light for photosynthesis yet.
Why does fruit help dispersal?
Seeds that fall beneath the parent compete with it for water, light and mineral ions. Fruits help seeds travel.
| Dispersal | Fruit or seed feature |
|---|---|
| Wind | Light, flattened or winged, or with a parachute of hairs |
| Animal (eaten) | Bright, fleshy, sweet; seeds pass through the gut undamaged |
| Animal (carried) | Hooks that catch on fur |
| Explosive | Dry pod that dries, twists and splits, flinging seeds |
Worked example
A pea flower has an ovary containing 8 ovules. After pollination and fertilisation, 6 ovules are fertilised.
The pod is later opened. How many seeds will it hold, what is the pod, and what happened to the other 2 ovules?
Step 1, one seed per ovule: each fertilised ovule becomes one seed, so 6 fertilised ovules give 6 seeds.
Step 2, the pod: it is the developed ovary wall, so the pod is the fruit.
Step 3, the other ovules: 8 − 6 = 2 ovules were not fertilised, so they did not become seeds. They shrivel and stay small.
Answer: 6 seeds inside a pod (the fruit); 2 ovules did not develop.
The mistake to watch for
A common slip is to say the ovary becomes the seed.
Mistaken answer: “After fertilisation the ovary becomes the seed and the ovule becomes the fruit.”
The student swapped the two parts. The ovary is the larger chamber, so it becomes the larger structure, the fruit.
The correction: the ovule is inside the ovary, and the contents become the seeds. The container becomes the fruit. Picturing the pod with seeds inside it makes the order obvious.
Check yourself
Answer on paper, then open each answer.
1. Name the part of the flower that becomes (a) the seed and (b) the fruit.
Show answer
(a) The ovule (fertilised). (b) The ovary (its wall).
2. A fruit has 12 seeds. How many ovules were fertilised?
Show answer
12, because one fertilised ovule becomes one seed.
3. A fruit is covered in small hooks. How is it likely dispersed, and how does this help the plant?
Show answer
By animals, because the hooks catch on fur. The seeds are carried away from the parent, so there is less competition for light, water and mineral ions.
Where this leads next
Seed formation is the sexual route to new plants. To compare it with plants that copy themselves, go to comparing sexual and asexual propagation. Our teachers use diagrams like these in online one-to-one Biology tuition so that structure and function stay linked.