This
reduces competition between
the parent plant and the seeds.
It reduces overcrowding
It provides opportunities
to spread the plant to new localities.
Some plants use the fruit
to enable dispersal while other plants use the seed only. Can you think of
three examples each of plants that use fruit dispersal and seed dispersal?
There are at least four
types of seed dispersal. These are wind dispersal,
animal dispersal, self-
dispersal and water dispersal.
Wind
Dispersal
As you
can see the sycamore fruit has the shape of a
helicopter blade so it helps to carry the
heavier seeds away from the parent flower.
Similarly the light fluffy
seeds of the dandelion help to carry the heavier seeds away from the parent
plant.
2. Animal
Dispersal
Animals
aid dispersal by either carrying the fruit or seeds on the outside of their
bodies or by eating the seeds and passing them out with their droppings.
Some
birds eat the fruit and then throw away the seeds.
Seeds
or fruit carried on the surface of animals often have hooks to attach it to
the coat of the animal.
Stickybacks
and thistles are common examples.
3. Self-Dispersal
This
can involve an explosion of the fruit which then throws the seeds away from
the fruit.
Examples
of plants that use this mechanism are the squirting cucumber and the pea plant.
Can you
find out how each of them disperses their seeds?
4. Water
Dispersal
The seeds
or fruits are dropped from the plant into the rivers, lakes or seas.
They,
being less dense than water, float and some of them can germinateif, on being
washed up on land, the conditions are favourable.
