Force, Motion
and Energy
Forces that affect motion…
Turgor Pressure:
Plants cells
have larger
vacuoles
because
they have
to store all
of the food
they make.
This
plant is
more
rigid!
This
plant is
more
wilted!
If a plant cell is immersed in a solution that has a higher salt
concentration than that of the cell, water will leave the cell.
The loss of water from the cell will cause the cell to lose the
pressure exerted by the water in the plant cell’s vacuole,
which is called turgor pressure.
If the cell
membrane
becomes
damaged,
it will lose
the ability
to control
what goes
in and out
of the cell.
Turgor Pressure in your skin:
Types of tropisms:
– Phototropism: response to light
This is why people turn their house plants so
they won’t lean.
– Thermotropism: response to temperature
The plants leaves curl
in response to the
temperature.
– Hydrotropism: response to water
The roots grow
toward the water
– Geotropism: response to gravity
The roots grow
downward due to the
force of gravity.
Geotropism
• The growth of a living organism in
response to gravity, as the downward
growth of plant roots.
• Roots display positive geotropism when
they grow downwards, while shoots
display negative geotropism when they
grow upwards.
Geotropism
A corn kernel was planted face down and this was the
result. You can see how it started to grow downwards
and then responded to the external stimulus of the sun
and grew upwards.
The root system started to grow upwards toward the
sun and then responded to gravity (geotropism) and
began to grow downwards.
For a plant to be planted in an upside down
planter like this the roots must be started
first. Why must the roots must be started
first in a regular planter?
Well because…
If you just planted the plant
upside down first the roots
would grow downward as
well which would kill the
plant. Geotropism is what
would cause the plants
roots to grow downward.
You must start the plant first so the
roots will grow correctly and then just
the plant itself will grow downwards.
Emergence of Seedlings:
Seeds respond to stimuli (internal and external).
Geotropism is where a seed
It takes force and
and its roots respond to the
pressure for the
force of gravity. This forces
plant to push out
the roots to grow downward.
of the ground.
Is this an internal or external Gravity is an
external stimulus!
stimulus?
Another external stimuli
to the plant is the sun.
The plant responds to the
sun by growing upwards.
Forces that affect motion…
• A force is a push or a pull.
• Work is done when a force moves an object.
• A seedling: pushing up the dirt :: a person: rolling a boulder up a hill
It takes MORE force
to move something
straight up
LESS force is used to move
something up a ramp or
inclined plane
Forces that affect motion…
• Seeds sprout
because the force
of water pressure
(also called turgor
pressure) inflates
the emerging
shoot. The force
of the shoot
straightening pulls
the seed leaves
above ground.
Forces that affect motion…
• Turgor Pressure, and Tropisms are all forces that
affect the motion of plants and its cells.
PHOTOSYNTHESIS in plants
GEOTROPISM
in roots
THERMOTROPISM in
HYDROTROPISM
plants leaves when it is in roots
cold
TURGOR Pressure in
celery and potato