1. Ch. 25: Plant Responses & Adaptations

2. 25.1: Hormones & Plant Growth
Chemical substances that control a plant’s:
Patterns of growth & development
Responses to environmental conditions
HORMONES

3. Tropisms: responses to external stimuli
25.2: Plant Responses
Tropisms: responses to external stimuli
Examples  Gravity
Light
Touch

4. GRAVITROPISM (geo)
Roots:
Shoots:

5. Phototropism

6. Thigmotropism

7. Other Responses: Rapid = Venus flytrap
Photoperiodism = seasonal activities
Winter dormancy = leaves fall

8. 25.3: Plant Adaptations Aquatic Environments : Hydrophytes
Tissues with large air filled spaces
“Knees” – roots above water
Floating seeds

9. Salt-Tolerant : Halophytes
Special salt-tolerant roots
Leaves = tissue to pump out salt

10. Desert Plants : Xerophytes
Extensive roots quick absorption
Small leaves reduce H2O loss
Thick stems store H2O, Photosynthesis

11. Epiphytes = not parasites, grow on other plants

12. Chemical Defenses
Poisons against insects
Human uses