Fertilisation and Germination in Plants

What is fertilisation?

The fusion of gametes

How does fertilisation occur in plants?

1. A pollen grains stick lands on the stigma of a flower, usually with help from insects or the wind

2. A pollen tube grows out of the pollen grain and down through the style to the ovary and into the ovule

3. A nucleus from the male gametes moves down the tube to join with a female gamete in the ovule. Fertilisation is when the two nuclei fuse together to make a zygote. This divides by mitosis to form an embryo.

4. Each fertilised female gamete forms a seed. The ovary develops into a fruit around the seed.

What is germination?

When seeds start to grow

What does a seed require to start germinating and what does it do before?

A seed will often lie dormant until the conditions around it are right for germination. Seeds need the right conditions to start germinating.

What conditions do seeds need to start germinating?

WATER - to activate enzymes that break down food reserves in the seed

OXYGEN - for respiration, which transfers the energy from food for growth

A suitable TEMPERATURE - for the enzyme inside the seed to work. This depends on what type of seed it is.

Where do germinating seeds get energy from?

Food stores

How do germinating seeds get energy?

1. A developed seed contains an embryo and a store of food reserves, wrapped in a hard seed coat

2. When a seed starts to germinate, it gets glucose for respiration from its own food store. This transfers the energy it needs to grow.

3. Once the plant has grown enough to produce green leaves, it can get its own food for energy form photosynthesis