4.5 Fertilization and germination
Summary: A pollen grain, carried by either the wind or an insect, lands on a stigma. If this stigma is from the correct species, it grows a pollen tube down the style. This allows the pollen nucleus to join… Tags: science oxford-science student-book-7 biology Created: 2026-05-19 Last Updated: 2026-05-19
Key words After this topic, you will be able to:
- describe the process of fertilization in plants
- describe how seeds and fruits are formed
- describe the main steps in germination.
Think back
- Which part of a flower produces pollen?
- What is the function of the stigma?
- What does a plant need to grow? Key idea Fruits contain seeds that can grow into new plants. Key words fertilization, fruit, seed, germination Have you ever grown a plant from a seed? Seeds need water, oxygen, and a warm enough temperature to start to grow. A plant only needs Light once it has grown its first leaf. All the nutrients a seed needs are stored inside the seed.
How do plants make seeds?
A pollen grain, carried by either the wind or an insect, lands on a stigma. If this stigma is from the correct species, it grows a pollen tube down the style. This allows the pollen nucleus to join with the ovule nucleus. The process is called fertilization. Figure 1 shows the main steps in fertilization in plants.
Figure 1Fertilization happens when pollen lands on a stigma. Full text alternative to the content
A Describe what happens during fertilization in plants.
After fertilization, the ovary develops into the fruit. The ovules become seeds. A fruit is normally the sweet and fleshy product of a plant that can be eaten as food. All fruits contain seeds.
B Name the organ in the flower that becomes the fruit.
What is inside a seed?
Most seeds have a similar structure, which you can see in Figure 2. However, they often have different shapes, sizes, and colours.
Figure 2The structure of a seed. Full text alternative to the content
What do seeds need for growth?
When a seed starts to grow, it is called germination. A seed needs three things to germinate:
- Water – this allows the seed to swell up (expand) and the embryo to start growing.
- Oxygen – this is used for Respiration, transferring Energy for germination.
- Warmth (a warm temperature) – this speeds up reactions in the plant, and speeds up germination.
C List the three factors needed for germination.
How does a plant grow?
Figure 3 shows the main steps in germination.
Figure 3Seeds need lots of water to grow into a plant. Full text alternative to the content
Working scientifically Design an investigation to test whether warmth, oxygen, and water are required for germination. What equipment will you need? What method will you use? What variables will you keep the same, change, and control?
Stretch zone
- Copy and complete the sentences. During fertilization/germination, the nucleus of the pollen/stigma grain and the nucleus of the ovary/ovule join together. The ovary then develops into the fruit/seeds, and the ovules become fruit/seeds. To germinate/pollinate, the seed needs water, cold/warmth, and oxygen.
- Describe what happens after the ovule is fertilized.
Stretch zone
- To produce new plants, seeds have to germinate. Explain two ways to Speed up the rate of germination in seeds.