(3.4-3.6) Fertilisation + Germination

What occurs after pollination?

a pollen tube forms from where the pollen has met the stigma

to deliver the male nucleus to the egg/ovum

in the ovary.

What is a pollen tube?

a tube that grows down the style to the ovary

through which the pollen grain travels

it enters the ovary through the micropyle

What is the micropyle?

a small opening in the surface of the ovule

When does fertilisation occur?

when the pollen nucleus and the ovum nucleus fuse together, forming a zygote

What occurs after fertilisation?

the ovule developed into a seed

the parts of the flower around the ovule becomes a fruit, containing seeds.

How do fruits provide a method of seed dispersal?

animals eat fruit and spread the seeds through egestion

some fruits have hooks that get caught in the fur of animals

Describe the process of double fertilisation. (unique to flowering plants)

One nucleus fuses with the egg → zygote

The other pollen nuclei fuse with the polar nucleus → triploid endosperm

What function does the triploid endosperm perform?

acts as a food store for the zygote, containing starch- inside the seed

Where does each part of the fruit come from in the ovary?

Embryo in center

seed coat (ovule)

fruit (ovary)

What is germination?

the beginning of seed growth

What conditions are needed for germination? Why?

Water

• swells seed to breaks seed coat

• activated enzymes needed for growth

  • they need to be in solution

Oxygen

• needed for respiration → energy

Warmth

• boosts enzyme activity + improves germination (till optimum)

Describe the events in the seed during germination.

embryo → seedling

• cotyledons (embryonic leaves) store food

• provide energy until plant can photosynthesise

Describe the structure of the seed.

Seed coat around it (testa)

Plumule + Radicle

Micropyle (where water enters)

Describe the set up for the experiment to investigates the practical for germination.

1. 4 test tubes with 10 cress seeds on cotton wool

A- dry wool

B- moist wool (control)

C- cover with water + add layer of oil

D- moisten wool + put tube in fridge

2. Keep A/B/C in 20 degrees C

3. Keep B+D moist

4. Compare the number of seeds germinated.

Result: only B should germinate