1. Plant Tropisms
All living organisms are sensitive to changes in their surroundings. Plants are sensitive to light, moisture and gravity.

2. Plant Tropism Notes TROPISM:
the movement or growth of a plant in response to a stimulus
POSITIVE/NEGATIVE
*Picture and Definition*
PHOTOTROPISM
GEOTROPISM
HYDROTROPISM
POP QUIZ 3.

3. Types of Tropisms Positive Tropism—growth towards the stimulus
Negative Tropism—growth away from the stimulus
Plant is growing TOWARDS the light
Stem is growing AWAY from the center of the Earth (against gravity)

4. Phototropism
Phototropism: the growth of a plant in response to LIGHT

5. How does Phototropism work?

6. Geotropism or Gravitropism
Geotropism: (also called gravitropism) the growth of a plant in response to gravity

7. Positive and Negative
Negative Geotropism: Plant stems growing upward away from the center of the Earth.
Positive Geotropism: Downward growth of plant roots (towards the center of the Earth).

8. What direction do you think the roots are growing?

9. Hydrotropism
Hydrotropism: the growth of a plant in response to moisture

10. Tropism Video Clips
Time lapse fast growing corn, roots and leaves growing
Plant Physiology: Phototropic Response

11. TROPISMS POP QUIZ!
1. What is the external stimulus that is responsible for the response of the plant shown in this illustration? A) Gravity B) fresh air C) lack of water D) sunlight

12. 2. What are the two external stimuli shown in this illustration to which the roots are responding?
A) light and water
B) gravity and light
C) water and gravity
D) soil temperature and gravity

13. 3. Which tropism is best illustrated?
Geotropism
Hydrotropism
Phototropism

14. 4. Which tropism is best illustrated?
Geotropism
Hydrotropism
Phototropism

15. 5. Which tropism is best illustrated?
Geotropism
Hydrotropism
Phototropism