3. • As the pollen has no ‘tail’ to swim to the ovary of a plant, in order to
reach the ‘female’ nucleus in the ovary it has to grow a pollen tube
• This only happens if the pollen grain has landed on the right kind of
stigma (i.e. of the same species as the flower the pollen came from)
• The nucleus inside the pollen grain slips down the tube as it grows
down the style towards the ovary
4. • The ovary contains one or more ovules which each contain an ovum
with a female nucleus that a male pollen nucleus can fuse with
• Once the nuclei (pl) have joined together, that ovule has been
fertilised and a zygote has been formed
• The zygote will start to divide and eventually form a seed within the
ovule
5. • As different plants have different numbers of ovules, this explains why
different fruits (which develop from the ovary) have different
numbers of seeds (which develop from the ovules)
6. The growth of the pollen tube
• The nucleus inside the pollen grain moves down the tube as the tube
grows down the style towards the ovary (which contains the ovule
that, in turn, contains the ovum)
• Once the nucleus of the pollen grain and the nucleus of the ovum
have fused (joined together), that particular ovule has
been fertilised and a zygote has been formed
• The zygote will then start to divide (it is the structure that eventually
develops into an embryo plant)
7.
8.
9. Seed and fruit formation
• After fertilisation, the ovule (that contains the zygote) develops into
the seed
• The wall of the ovule develops into the seed coat, known as the testa
• The parts of the flower surrounding the ovule (mainly the ovary
walls) develop into the fruit, which contains the seeds
10. • The fruit provides a mechanism for seed dispersal (getting the
seeds away from the parent plant)
• Some fruits are eaten by animals, which then disperse the seeds in
their droppings (the tough outer coat of seeds stops them from being
digested)
• Some other fruits have sticky hooks that get caught in the fur of
passing animals
11. Germination
• Germination is the start of growth in the seed
• The seed contains the zygote (the fertilised egg cell),
which divides into cells that then develop into the embryo plant
• When the seed germinates, this embryo begins to grow into the
young seedling
12.
13. Structures known as cotyledons surround the embryo
• Some plants have one cotyledon, whereas others have two
• The cotyledons contain food reserves that supply the young seedling
with food (and, therefore, energy for growth) when the seed starts to
germinate
• The cotyledons fulfil this role until the young plant grows its own leaves and
becomes capable of making its own food via photosynthesis
14. • After taking in water, the seed coat (testa) splits
• This leads to the production of the plumule (the first emerging shoot)
and radicle (the first emerging root)
15. • Fertilization: The fusion of the male and female gametes.
• Embryo: the structure which contains shoot and root ( plumule and
radicle) and develops into seedling.
• Cotyledons: the food store of a seed.
• Fruit: a fertilized ovary and has the function of dispersing the seed.
• Germination: development of a seed to a new plant.
