Plant Tropisms

Why do you think trees and plants grow up toward the sky?

• To reach the clouds

• to gather more air

• to gain more sunlight

• to beat gravity

What is a plant's reaction to an external stimulus?

• tropisms

• reactions

• responses

• growth

If you were walking through the woods and you were desparately hungry, would you eat a plant that displayed thigmotropism?

• Plants that move could taste better.

• Moving plants are not my "cup of tea."

• I would not eat a plant in the woods if it moved or if it didn't move.

• What is thigmotropism?

We know that roots grow out to search for water. However, what is it called that roots are growing down?

• Thigmotropism

• Phototropism

• Soiltropism

• Gravitropism or Geotropism

Why do you think a plant expresses phototropism?

• The stomata want to capture more carbon dioxide.

• The stomata want to capture more oxygen.

• The chlorphyll want to capture lots of solar energy from the light of the sun.

• The mitochondria want to capture lots of solar energy from the light of the sun.

Label the correct tropisms.

a

b

c

d

gravitropism

Hydrotropism

Phototropism

Thigmotropism

LOOK AT THE DIAGRAM.

What reaction to an external stimulus is the plant responding to underground?

• Phototropism

• Thigmotropism

• Heliotropism

• Hydrotropism

There is a tropism called thermotropism. What do you think this might be a response to?

• Plant growth is affected by temperature. 

• Plant roots grow towards a water source. 

• Plants grow towards a light source, like a stem bending towards sunlight. 

• Plant growth is influenced by specific chemicals, like pollen tubes growing towards the ovule.