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Plants &
External
Stimuli
When someone shines a bright light
in your face, how do you respond?
?
Essential Question
How do plants respond to external stimuli?
Dormancy:
• A period of time when growth or activity of a
plant or seed stops due to changes in
temperature or amount of water
• This allows the plant to survive in certain
environments
• Seeds will grow in conditions that are favorable
(good) for survival.
• Ex. Leaves fall from tree in Fall and leaf buds
come back in Spring; Apples fall to ground in
Fall and don’t grow until Spring.
How do you think plants loosing their
leaves helps them to survive?
Phototropism
• A plant grows or moves in response to
light.
• Illustrate phototropism.
How would moving towards light
help a plant survive?
Gravitropism:
• A plant grows or moves in response to
gravity
• Also called geotropism.
• Illustrate gravitropism.
How would growing with gravity
help a plant survive?
Hydrotropism
• A plant moves or grows in response to
water.
• Illustrate hydrotropism.
How would growing towards water
help a plant survive?
Thigmotropism
• A plant moves or grows in response to
touch.
• Illustrate thigmotropism.
How would growing towards
something it touches
help a plant survive?
Tropisms
How do plants grow in space?
Setting up the experiment
How do plants grow in space?
Experiment Results
What’s the tropism?
What’s the tropism?
What’s the tropism?
What’s the tropism?