Tropism refers to the growth movements of plants in response to environmental stimuli. There are several types of tropisms: 1) Phototropism is the growth of plants toward light to maximize photosynthesis. 2) Gravitropism causes roots to grow downward and shoots upward in response to gravity. 3) Thigmotropism is the growth of plants in response to touch, such as vines wrapping around trees.

1. Plants Move

2. TROPISM
is a biological
phenomenon,
indicating growth
or turning
movement a plant
makes in response
to an
environmental
stimulus

3. Tropism
http://plantsinmotion.bio.indiana.edu/plant
motion/movements/tropism/tropisms.html

4. Phototropism
Movement of plants toward light to maximize amount
of sun for photosynthesis to make their food.
Heliotropism
http://www.youtube.com/watch?NR=1&v=KQOC_bPr
qFs&safety_mode=true&persist_safety_mode=1

5. Gravitropism
Movement of plants in
response to gravity
Positive is toward gravity
(roots)
Negative is away from
gravity (shoot: stems and
leaves)
http://www.youtube.com/w
atch?v=mYZXax8V_L0&featu
re=related&safety_mode=tru
e&persist_safety_mode=1

6. Hydrotropism
Movement by plants toward water.
Seen in roots “searching” and growing
toward water which is needed for
photosynthesis and to support cell
structure.
http://virtualastronaut.tietronix.com/textonly
/act25/text-plants.html

8. Thigmotropism
Plants moving in response to touch.
Seen in vine plants as they wrap around other
plants or structures to support leaves as they
grow higher and higher to reach the sun to
make more food (photosynthesis).
http://www.youtube.com/wat
ch?v=8HeedWWe6VA&featur
e=related&safety_mode=true
&persist_safety_mode=1

9. Plant Tropisms
Tropism: the way a plant grows in response to
stimuli in the environment.
1) Phototropism: growth response to light
 Plants bend towards light
2) Gravitrophism: growth response to
gravity
 plant roots grow down with
gravity, shoots (stems) grow up
against gravity and out of the soil.
3) Thigmotropism: growth response to
touch
 vines grow up around trees, Venus
flytrap closes when leaves are
touched

10. Slide # 23
What type of tropism is shown in these pictures?
B
A.
C D E. F

11. Slide # 23
What type of tropism is shown in these pictures?
Phototropism
Gravitropism
Phototropism Thigmotropism Gravitropism Thigmotropism

12. Review
Adaptations for Life on Land
Leaves – absorb energy from sun;
centers for photosynthesis and
gas exchange
 Roots – anchor plants; absorb
H2O & minerals from soil
 Stems – hold plant upright;
transport food & water along
the plant
 Flowers – produce sperm & eggs
for reproduction in angiosperms
 Seeds – protect embryo from
damage and water loss;
dispersed away from parent
plant
 Fruits – method of seed dispersal
in flowering plants