1. Plant Tropisms
The movement or growth of
a plant in response to a
stimulus…

2. ENVIRONMENT
The environment of an organism is
made up of all of the factors that affect it.
A habitat is a zone with a certain range
of factors, such as a savannah.
An organism has adaptations that help it
survive in its habitat. The better adapted
it is, the more chance it has of successful
reproduction – survival of the fittest.

3. Plant Responses (Tropisms)
 Tropism is growth in response to an
external stimulus (Stimulus is a factor
that elicits a response).
 Positive tropism: Plant growth toward
a stimulus (Ex. water, sunlight)
 Negative tropism: Plant growth away
from a stimulus (Ex. spilled gas, toxins,
too much sun or not enough)

4. So, plants can move to respond to the
environment.
The stimuli for growth may be:
Light Temperature
Water Chemicals
Gravity Touch

5. Some of these ways are:
 Phototropism
 Geotropism
 Hydrotropism
 Thigmotropism

6. Phototropism
 Phototropism is a
change in the growth
of a plant in response
to light.
 The stalk displays
positive phototropism
growing towards the
light.

7. Why?
Maximize amount of sun for
photosynthesis to make their food.

8. Positive
Phototropism
Plant
Illustrate phototropism on your paper.
Label your illustration as you would any scientific drawing.
(See rules on your paper!)
This stalk displays
positive
phototropism
growing towards
the light.

9. Time Lapse of Plants
Following Light
https://www.youtube.com/watch?v=wjZ1UYwrO8A

10. Corn
Dance
After 3 days of growth in darkness, the pot of corn seedlings in this movie
were exposed to light from a single light bulb placed in the center of the pot
just above the seedling. The plants were then imaged at 10 min intervals for
about 18 hours. For the first 14 hours the seedlings appear to be dancing to
the light as they maintain phototropic curvature. Since geotropism is
simultaneously affecting the seedlings, the curvature that develops is a
compromise between the opposing light and gravity responses. After 14
hours, the point light source was turned off and diffuse room lighting was
turned on, at which point geotropism becomes the dominant stimulus and the
seedlings quickly return to a vertical orientation. Frame playback is at 12
frames per sec.
https://www.youtube.com/watch?v=RZDwoteRuqA

11. Geotropism
(Gravitropism)
 Geotropism is a change
in the growth of a plant
in response to gravity.
 The stalk displays a
negative geotropism
growing away from
gravity.
 The roots display a
positive geotropism
growing towards gravity.
Negative
Positive
Write the definitions and illustrate
them. Label your illustration as you
would any scientific drawing.

12. Negative
Geotropism
Illustrate geototropism on your paper.
Label your illustration as you would any scientific drawing.
(See rules on your paper!)
This stalk displays
NEGATIVE
phototropism
growing away from
the gravity.

13. Positive
Geotropism
Illustrate geototropism on your paper.
Label your illustration as you would any scientific drawing.
(See rules on your paper!)
The roots display
POSITIVE
phototropism
growing towards
gravity.

14. Gravitropism
http://www.youtube.com/watch?v=8SkKuwbmR5Y&feature=related&safety_mode=true&persist_safety_mode=1
Why?
Allows plants to grow properly
and get nutrients and sunlight

15. Geotropism
(Gravitropism)
https://www.youtube.com/watch?v=mYZXax8V_L0

16. Phototropism and
Geotropism Time Lapse
Montage
https://www.youtube.com/watch?v=F3Oj2er-91s

17. Hydrotropism
 Hydrotropism is a
change in the growth
of a plant in response
to water.
 The roots display a
positive hydrotropism
growing towards
water.
Positive
Water
Write the definition and illustrate it.
Label your illustration as you would
any scientific drawing.

18. Hydrotropism
 Why?
 Roots search for and
grow toward water,
because it is needed
for photosynthesis
and to support cell
structure.
Positive
Water
Write the definition and illustrate it.
Label your illustration as you would
any scientific drawing.

19. Thigmotropism
 Thigmotropism is a movement in which an
organism moves or grows in response to
touch or contact stimuli.
 Thigmotropism
usually occurs when
plants grow around a
surface, such as a wall,
pot, or trellis.
illustrate thigmotropism.
Label your illustration as you would
any scientific drawing.
https://www.youtube.com/watch?v=m2xKjA69jNM

20. Thigmotropism
 Why?
 to support leaves
as they grow higher
to reach the sun to
make more food
(photosynthesis).
Label your illustration as you
would any scientific drawing.

21. NASTIC RESPONSES are fast, reversible
movements and are non-directional. The
movement can be caused by changes in
turgor pressure or changes in growth.
http://www.youtube.com/watch?v=O7eQKSf0LmY
Hungry Venus flytraps snap shut on a
host of unfortunate flies. But, despite its
name, flies aren’t the flytrap's only meal.
As long as its prey is roughly the right
size and touches two of its hairs within
twenty seconds, the plant will dine on
any insect or spider that comes its way.
Glands in the lobes then secrete
enzymes that break the dinner down
into a digestible soup. Ten days later,
the trap pops open to reveal nothing but
a dried out husk.
Venus Flytraps: Jaws of Death - BBC One

22. Mimosa Pudica –
The Sensitive plant
https://www.youtube.com/watch?v=BLTcVNyOhUc

23. Plants
in Action
 We tend to think of plants as being essentially
stationary incapable of movement other than that
generated by the wind. But all plants do move as
they grow and respond to aspects of their
environment.
https://www.youtube.com/watch?v=zmxY6aD7ltM