Seed Dispersal
The fruit often helps to disperse (spread) the
seeds.
It is important that seeds be dispersed far from
the parent plant so they do not have to compete
for water, space and nutrients.
There are four main methods of seed dispersal:
Explosions
Water
Wind
Animals
The seeds of flowering plants vary in size.
Some are as small as grains of salt
(Foxglove), while others may be almost
the size of golfballs (Horse Chestnuts).
The difference in size reflects differences in
the amount of food stored inside the seed
for the baby plant.
Usually, the larger the seed, the more food
reserves it contains.
There is a down-side to having large seeds.
The larger and heavier the seeds, the more
difficult it becomes to disperse by wind, or
explosions. Larger wind-dispersed seeds
need parachutes or wings to help keep them
floating.
The largest and heaviest wind-dispersed
seeds, cannot rely on parachutes to keep
them floating.
Instead they have developed a wing which
causes them to spin through the air like
mini helicopters.
The biggest seeds of all cannot possibly be
dispersed by the wind. Large seeds such
as nuts, are often dispersed by animals
which collect them to eat.
Animals hardly ever eat all the seeds. Some
will usually be overlooked, leaving them to
germinate wherever they have been left
when conditions are right.
Explosion…...
• Some plants distribute their seeds by ‘popping’
them out. Example: Gorse
Water……….
Some plants that live near water have fruits
that float and are carried by water.
Example: Coconuts
Wind.........
Seeds dispersed by the wind must be light
and small.
Plants have developed different adaptations
to help the seeds be released and to stay
in the air for longer:
1. Salt shaker type
The fruit becomes a
dry hollow container
with holes. The
containers are shaken
by the wind,
scattering the seeds.
Example:
Poppy seeds
2. Parachute type
Feathery hairs help the
seed to float on the
wind.They can often
be carried long
distances in this way.
Example: Ragwort
3. Winged type
Wings on the fruit make
it spin as it falls. This
spinning delays its fall
so that the wind may
carry it some distance
away.
Example: Sycamore
Animals.........
1. Some plants have
hooks to which the
seed is attached.
These hooks easily
get caught in the fur
of passing animals.
Example: Burdock
2. The small hard seeds
inside many fruit,
pass through the gut
of animals and and is
expelled in the
droppings.
Example: Blackberries
1.How are these seeds dispersed?
2. How are these seeds dispersed?
3.How are these seeds dispersed?
(2mm long)
4. How are these seeds dispersed?
5. How are these seeds dispersed?