1. Plant Form and Function
Learning Goal: How are plants structurally adapted for survival?
Analyzing how plants detect and defend themselves against herbivores and environmental stresses (Ch 39)
Refer to pg in Holtzclaw Ch 39 in Campbell Media resources

2. Try This! (from last year)
In double fertilization, how is the endosperm formed?
The fusing of two sperm and an egg
From the epidermis
From the fertilization of the egg
From the zygote during development
From the fusing of a sperm with two polar bodies

3. Try This! In double fertilization, how is the endosperm formed?
The fusing of two sperm and an egg
From the epidermis
From the fertilization of the egg
From the zygote during development
From the fusing of a sperm with two polar bodies

4. Analyzing how plants detect and defend themselves against herbivores and environmental stresses (Ch 39)
You must know:
The three steps to a signal transduction pathway
The role of auxins in plants
The survival benefits of phototropism and photoperiodism use changes in environment to modify plant growth and behaviour
How plants respond to attacks by herbivores and pathogens

5. Try This!
Both plants and animals respond to environmental stimuli. Which of the following statements are true and which ones are false?
The processes by which plants and animals perceive environmental changes are equally complex.
The processes by which plants and animals perceive environmental changes are often homologous.
Unlike animal hormones, plant hormones act only locally.
Both plants and animals have physiological cycles called circadian rhythms.

6. Try This!
Both plants and animals respond to environmental stimuli. Which of the following statements are true and which ones are false?
The processes by which plants and animals perceive environmental changes are equally complex. TRUE
The processes by which plants and animals perceive environmental changes are often homologous. TRUE
Unlike animal hormones, plant hormones act only locally. FLASE
Both plants and animals have physiological cycles called circadian rhythms. TRUE
Plant hormones can be broadcast

7. Try This!
What are the morphological differences in dark-grown plants and light-grown plants?

8. Try This!
What are the morphological differences in dark-grown plants and light-grown plants?
Dark- grown have
long stems
underdeveloped roots
unexpanded leaves
shoots lack chlorophyll
But, WHY?

9. How does this potato change its growth when there is light?

10. How does this potato change its growth when there is light?
Via the Signal Transduction Pathway!

11. How does this potato change its growth when there is light?
Via the Signal Transduction Pathway!
The signal (light) is transduced to a response (greening)

12. Signal Transduction - Review
Reception
Transduction
Response

13. Signal Transduction - Review
Reception: Receptors undergo changes in shape due to an environmental stimulus
Ex) phytochrome proteins changing in response to light

14. Signal Transduction - Review
Transduction: Amplification of signal through a multistep pathway
Allows small signal to produce large cellular response
Uses protein kinases (phosphorylation cascade) and second messengers (Ca2+ and cAMP)

15. Signal Transduction - Review
Response: Two ways response is accomplished:
Transcriptional Modification:
↑ or ↓ mRNA production (turning genes on/off)
Post-Translational Modification:
Activates existing enzyme molecules

16. Signal Transduction Proteins include: Photosynthesis enzymes
Plant growth hormones
Auxin levels lower to slow stem growth (focus on leaf growth)

17. So…. What was AUXIN?
A plant hormone…
Yes, plants have hormones too!

18. Examples of Plant Hormones
Auxins – stimulate elongation of cells within young developing shoots
Cytokinins – stimulate cell division
Gibberellins – stimulate stem elongation, pollen, fruit, seed development
Abscisic acid – promotes stomatal closure during drought stress
Ethylene (gas!) – fruit ripening, leaf abscission

19. Plant Hormones
Hormones: chemical messengers that coordinate the different parts of a multicellular organism
Tropism: Plant growth response toward or away from a stimulus
Phototropism
Gravitropism
How does this benefit survival?

20. Phototropism - Mechanism

21. Phototropism - Mechanism

22. Phototropism - Mechanism

24. Actions of hormones…
Photoperiodism – physiological response to a photoperiod (relative lengths of day and night)
Example: Flowering
Short day plants
Long day plants
Day-neutral plants
Circadian rhythms – physiological cycles that have a frequency of about 24 hours

25. Responses to Mechanical Stimuli
Mimosa Plant

26. Herbivore Defense
Video Clip

27. Think:
Illustrate this statement with an example: “A plant generally responds to environmental cues by adjusting its pattern of growth and development.”

28. How do plants detect and defend themselves against herbivores and environmental stresses?
Do you know?
The three steps to a signal transduction pathway
The role of auxins in plants
The survival benefits of phototropism and photoperiodism use changes in environment to modify plant growth and behaviour
How plants respond to attacks by herbivores and pathogens
Try # 1 p. 213, #1-4 p. 215 in Holtz