1. Plant Regulation
Chapter 39

2. Plant growth Plants respond to environment
Growth response to abiotic factors
Water, wind & light

3. Plant responses
Light
Gravity
Touch
Water
Temperature

4. Plant hormones Internal signal (developmental) Environmental signal
Chemical binds receptor
Physiological response
Developmental response
Reception-transduction-response
Regulate growth & development
New protein or activation of protein

5. Signal transduction pathway
CELL WALL
CYTOPLASM 1
Reception 2
Transduction 3
Response
Receptor
Relay proteins and
Activation of cellular responses
second messengers
Figure 39.3 Review of a general model for signal transduction pathways
Hormone or environmental stimulus
Plasma membrane

6. Potato plant de-etiolation (greening)
Figure 39.2 Light-induced de-etiolation (greening) of dark-grown potatoes
(a) Before exposure to light
(b) After a week’s exposure to natural daylight

7. De-etiolation (greening) response proteins
Potato response 1
Reception 2
Transduction 3
Response
Transcription factor 1
CYTOPLASM
NUCLEUS
Plasma membrane
cGMP
Protein kinase 1 P
Second messenger produced
Transcription factor 2
Phytochrome activated by light P
Cell wall
Protein kinase 2
Transcription
Light
Translation
Figure An example of signal transduction in plants: the role of phytochrome in the de-etiolation (greening) response (step 3)
Ca2+ channel opened
De-etiolation (greening) response proteins
Ca2+

8. Light response Photomorphogenesis:
Nondirectional light-triggered development
Change in form
Flower formation
Phototropisms:
Directional development
Trope (turn)

9. Plant hormones Auxin Cytokinins Gibberellins Brassinosteriods Ethylene
Abscisic acid

12. Auxin First plant hormone (IAA) Indoleacetic acid
Found in apical meristems of shoots
Promotes activity of vascular cambium
Promotes lateral root growth
Found in pollen, fruit development

13. Auxins Plasticity (soften) of plant Elongation of plant
Auxin moves from light exposed side
To shady side
Bends towards light

16. Auxins Synthetic auxins Prevent apples from dropping early
Berries on holly
Seedless tomatoes
Control weeds

17. Cytokinins Similar to adenine (purines)
Cell division & differentiation
Found in root apical meristems
Transported through plant
Lateral buds into branches
Inhibit lateral roots (auxin promotes)

18. Cytokinins Remove terminal bud Plant becomes bushier
Promotes lateral buds into branches
Auxin on cut surface
Inhibits lateral buds

19. Cytokinins Applied to cut leaves prevent aging
Florists spray on fresh cut flowers
Crown gall
Tumor growth on trees
Bacteria causes increased production of auxin & cytokinins

20. Gibberellins Stem elongation Enhances if auxin present
Found in apical portions of stems & roots
Apply to dwarf plants restores normal growth

21. Gibberellins Stimulate enzymes that utilize food during germination
Hastens germination
Fruit development
Helps space grape leaves (internodes)
Fruits have more space to grow

22. Brassinosteriods
Similar in structure to testosterone, estradiol, cortisol
Elongation & cell division
Bending of stems
Reproductive development
Delays senescence

23. Abscisic Acid In mature green leaves, fruit & root caps
Formation of winter buds
Induce seed dormancy
Controls stomata open/close

24. Ethylene Gas Suppresses stem & root elongation Hastens fruit ripening
Response to stress
Leaf abscission
Programmed cell death

25. Ethylene Mechanical stress on stem tip. Triple response
Enables a seedling to avoid an obstacle.

26. Ethylene
Commercially sprayed on green tomatoes
Hastens ripening

27. Light response Certain wavelengths of light Initiate biological change
Phytochrome:
Pigment containing protein
Pr (inactive form)
Pfr(active form)

28. Light response Inter-convertible forms Pr absorbs red light (660nm)
Converts to the active form Pfr
Pfr absorbs far red light (730 nm)
Converts to the inactive form Pr

29. Light response Acts as switching mechanism
Controls various light-induced events
Phytochrome exposed to red light
Pr is converted to Pfr
Triggering germination
Far-red light inhibits germination

30. Light response

31. Light response Determine plant spacing Pfr plant grows tall
Pr plant branches

32. Circadian clocks

33. Gravity response Gravitropism Response of plant to gravitational pull
Shoot negative gravitropic response
Roots positive gravitropic response

34. Gravity response Amyloplasts: Starch containing organelles
Maybe involved in sensing gravity
Stem located in the endoplasm
Root located in the root cap
Root cap is involved in sensing gravity

35. Touch response Thigmotropism Directional growth response
Direction of touch
Object, animal, wind
Thigmonastic
Responds in one direction
Despite where the contact is

36. Touch response Tendril touches an object Uneven growth
Wraps around the object
Fly trap
Touch hairs, closes (0.3 sec)

37. Turgor Movement Touch induces change in turgor Cells collapse
Causes leaf movement
Pulvini:
Multicellular swellings
Located base of leaf or leaflet

38. Turgor movement Environmental stimuli
Rapid loss of K+ out of half the pulvini cells
Water follows
Causes cells to be flaccid
Leaves fold in
Reverses in approx minutes

39. media\39_26MimosaLeaf_SV.mpg

40. Dormancy Survive environment extremes
Signals that initiate or terminate dormancy
Temperate regions dormancy occurs during winter (day-length)
Dry climates dormancy comes in summer (rainfall)

41. Plant defense First defense Dermal tissue system Cutin, suberin
Bark, thorns, trichomes

42. Plant defense Poisons Cyanide-containing compounds
Stops electron-transport
Cassava (African food)
Secondary metabolites
Alkaloids (caffeine, nicotine, cocaine, and morphine)

43. Plant defense Soy products produce Phytoestrogens
Similar in structure to estrogen
Decreased prostate cancer in Asian men
Help minimize menopausal symptoms

44. Plant defense Pacific Yew produces Taxol
Fights cancer especially breast cancer
Cinchona tree bark Quinine
Anti-malaria drug

45. Plant defenses
Toxic when metabolized by herbivore

46. Plant defense Allelopathy: When a chemical secreted by roots
Inhibits growth of other plants
Black walnut trees

47. Plant defense Plant is injured Cell death at location
Prevents further spread of pathogen
H2O2 & NO can be produced
Can cause harm to invader
Chemicals released to warn other plants of an invasion

48. Wasps