Transcript plant tropisms

Plant Responses to
the environment
“Tropisms”
Why is a sunflower called
a sunflower?
What is a Tropism?
 Tropism comes from the Greek word for
“Turning”
 So when an organism exhibits a tropism
it either has a positive turning (toward the
source) or a negative turning (away from
the source)
 Many organisms have tropisms
What kinds of tropisms do
plants have?
 Plants have 4 kinds of tropisms that we
will learn about
 Phototropism
 Gravitropism
 Hydrotropism
 Thigmotropism
Phototropism
 Photo means light
 So a phototropism is a turning
toward or away from light.
 Plants stems and leaves exhibit
positive phototropism, which
means they turn toward light
 Watch more phototropism videos
here
Gravitropism
 Gravi means gravity
 So a gravitropism is a turning
toward or away from gravity.
 Plant roots exhibit positive
gravitropism, which means
they turn toward gravity.
 Plant leaves and stems
exhibit negative gravitropism,
which means they turn away
from gravity
 Check out gravitropism videos
Hydrotropism
 Hydro means water
 So a hydrotropism is a
turning toward or away from
water.
 Plant roots exhibit positive
hydrotropism, which means
they turn toward water
Thigmotropism
 Thigmo means touch
 So a thigmotropism is a
turning toward or away
from touch.
 Some plant leaves and
stems exhibit positive
thigmotropism, which
means they turn toward
touch
 Check out more
thigmotropisms here
Plant Adaptations
When tropisms help survival
 Sometimes plants
can’t get all the
resources they need.
 Over long periods of
times tropisms
evolve into
adaptations for
survival
Plant Adaptations
When tropisms help survival
 Cacti have taken
hydrotropism to an
extreme!
 Cacti live in VERY dry, Very
hot conditions so they have
modifications to help them
cope with the weather
Plant Adaptations
When tropisms help survival
 Their roots are LONG and
shallow to seek out water
 They have also modified
their leaves down into to
tiny thorns to keep the
water from evaporating
 And their stems are filled
with vascular tissue to store
water
Plant Adaptations
When tropisms help survival
 Venus Fly Traps and
other carnivorous
plants have taken
thigmotropism to an
extreme!
 They live in nitrogen
poor soil and can’t
get enough nutrients
from the soil
Plant Adaptations
When tropisms help survival
 They use their touch
sensitive fibers to
know when an insect
lands on their traps
and then they close,
digest the insect and
suck up all the
delicious nitrogen
from the insect
 Check it out here
Question 1
 Which of the following is false about
tropisms?
 A. they can be positive or negative
 B. they only occur in plants
 C. they happen when organisms move
toward or away from something
 D. they are natural occurrences
Question 2
 What does positive phototropism mean?



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A. the organism moves toward light
B. The organism moves away from light
C. the organism moves toward the picture
D. the organism moves away from the
picture
Question 3
 What part of the plant has a positive
gravitropism?



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A. the roots
B. the stem
C. The leaves
D. the flowers
Question 4
 Which tropism would help a cactus
survive best?

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A. phototropism
B. geotropism
C. hydrotropism
D. thigmotropism
Question 5
 Which tropism is being displayed most
here?
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A. phototropism
B. geotropism
C. hydrotropism
D. thigmotropism
Question 6
 Which tropism is being displayed most
here?

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A. phototropism
B. geotropism
C. hydrotropism
D. thigmotropism
Question 7
 Which tropism is being displayed most
here?



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A. phototropism
B. geotropism
C. hydrotropism
D. thigmotropism
Question 8
 What adaptations does
this plant have?
 A. thick stem to store
water
 B. tiny leaves to conserve
water
 C. long root system to
search out water
 D. all of the above
Question 9
 Where would you most
likely find carnivorous
plants?
 A. nitrogen poor swamps
 B. nutrient rich rain
forests
 C. temperate forest
 D. all of the above