The Process of Fertilisation in Plants

Students lose easy marks by treating pollination and fertilisation as the same thing. They are two separate events that happen one after the other.

• Pollination is the transfer of pollen from an anther to a stigma. Pollen simply lands on the stigma — nothing has joined together yet.
• Fertilisation happens later and inside the flower. It is when the male nucleus fuses (joins) with the female nucleus inside the ovule.

So pollination just gets the pollen to the right place. Fertilisation is the actual joining of the two sex cells' nuclei to make a new individual.

A simple way to keep them apart:

	Pollination	Fertilisation
What moves?	The whole pollen grain	Only the male nucleus (down the pollen tube)
Where?	Anther → stigma (outside)	Inside the ovule
What happens?	Pollen lands on the stigma	Male nucleus fuses with female nucleus
Result	Pollen is in position	A fertilised ovule (becomes a seed)

Exam tip. If a question says "explain the difference between pollination and fertilisation", you must name where each happens and what fuses/lands. Saying "pollination is the start of fertilisation" is not enough.

Once a pollen grain has landed on the stigma (pollination), it cannot fertilise the ovule straight away — the ovule is hidden deep inside the ovary, with the long style in the way. The pollen solves this by growing a pollen tube.

Here is what happens step by step:

1. A pollen grain lands on the stigma.
2. The pollen grain grows a pollen tube out of itself.
3. The pollen tube grows down through the style, towards the ovary.
4. The pollen tube carries the male nucleus down inside it.
5. The pollen tube reaches an ovule inside the ovary.

The pollen tube is basically a delivery tube: its whole job is to carry the male nucleus all the way down to the female nucleus so the two can join. Without the pollen tube, the male nucleus could never reach the ovule.

Here is the journey labelled:

Exam tip. The marking phrase is "the pollen tube grows down the style to the ovule". Make sure the direction is right — down the style to the ovary/ovule, not the other way round.

When the pollen tube reaches the ovule, the actual moment of fertilisation takes place.

• The male nucleus (delivered down the pollen tube) fuses (joins) with the female nucleus inside the ovule.
• "Fuses" means the two nuclei join together to become one — this is the key word examiners want.
• The result is a fertilised ovule.

This is the single most important definition for spec 3.4:

fertilisation = male nucleus + female nucleus fusing inside the ovule

Notice that only the nucleus travels down the pollen tube — not the whole pollen grain. The pollen grain itself stays up on the stigma; it is the male nucleus that is carried down to meet the female nucleus.

Exam tip. Use the word fuse (or "join together"), and say male nucleus and female nucleus. Vague answers like "the pollen joins the ovary" do not score. The fusion happens inside the ovule.

Fertilisation is the trigger for seed and fruit formation. After the nuclei have fused, the flower changes:

• The fertilised ovule develops into a seed. Inside the seed is the new young plant (the embryo) plus a food store.
• The ovary develops into the fruit. The fruit grows around and protects the seed(s) and often helps with seed dispersal (spreading the seeds away from the parent plant).

A quick way to remember which becomes which:

Part of flower (before)	What it becomes (after fertilisation)
Ovule	Seed
Ovary	Fruit

So the full chain for spec 3.4 is:

1. Pollen lands on the stigma (pollination).
2. Pollen tube grows down the style to the ovule.
3. Male nucleus fuses with female nucleus (fertilisation).
4. Fertilised ovule → seed.
5. Ovary → fruit.

Remember: no fertilisation = no seed and no fruit. Fertilisation is essential for seed and fruit formation.

Exam tip. "Ovule → seed" and "ovary → fruit" are reliable marking points. Do not mix them up (a common error is saying the ovary becomes the seed).

It helps to see the whole process as one connected story, because exam questions often ask you to describe the events from pollination to seed formation.

1. Pollination — a pollen grain is transferred to the stigma and lands on it.
2. Pollen tube — the pollen grain grows a pollen tube down the style towards the ovary.
3. Delivery — the pollen tube carries the male nucleus to an ovule.
4. Fertilisation — the male nucleus fuses with the female nucleus inside the ovule.
5. Seed — the fertilised ovule becomes a seed.
6. Fruit — the ovary becomes the fruit, protecting and helping to spread the seed.

Keep two ideas crystal clear:

• Pollination ≠ fertilisation. Pollination is pollen landing on the stigma; fertilisation is nuclei fusing in the ovule.
• Two different "becomes". Ovule → seed, ovary → fruit.

Exam tip. A common 4–6 mark question is "describe how a flower produces seeds after pollination". Score full marks by giving the pollen tube growing down the style, the fusion of nuclei (fertilisation), and both outcomes — ovule → seed and ovary → fruit — in the correct order.