Control Systems in Plants - PowerPoint PPT Presentation

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Control Systems in Plants

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Control Systems in Plants Plant Hormones Coordinates growth Coordinates development Coordinates responses to environmental stimuli Plant Hormones Auxin (IAA ... – PowerPoint PPT presentation

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Title: Control Systems in Plants


1
Control Systems in Plants
2
Plant Hormones
  • Coordinates growth
  • Coordinates development
  • Coordinates responses to environmental stimuli

3
Plant Hormones
  • Auxin (IAA)
  • Cytokinins
  • Gibberllins
  • Abscisic Acid
  • Ethylene
  • Oligogaccharins
  • Brassinosteroids

4
Auxins
  • Stimulates stem elongation
  • Stimulates root growth
  • Stimulates differentiation and branching
  • Stimulates development of fruit
  • Stimulates apical dominance
  • Stimulates phototropism and gravitropism

5
Auxin Control
  • Auxin stimulates growth
  • Auxin block on right causes cells to elongate and
    the plant bends left
  • Auxin block on left causes cells to elongate the
    the plant bends right

6
Polar Transport
  • Auxin is transported from apex to shoot
  • Cell wall is acidic
  • auxin ion picks up H
  • diffuses across plasma membrane
  • Cytosol is neutral
  • auxon loses H
  • uses energy to pump out H to maintain pH
  • leaves cell through carrier proteins

7
Acid Growth Hypothesis
  • Proton pump stimulated by auxin which lower pH of
    wall
  • Hydrogen Ion activates Enzyme
  • Enzyme breaks hydrogen bonds in cellulose
  • Wall takes up water and elongates

8
Auxin Others
  • Promotes secondary growth by encouraging vascular
    cambium and secondary xylem
  • Promotes adventitious root at the base of a cut
    stem
  • Promotes fruit growth without pollination
    (seedless tomatoes)

9
Cytokinins
  • Stimulates root growth
  • Stimulates cell division and differentiation
    (with auxins)
  • more cytokinin - shoot buds develop
  • more auxin - roots develop
  • Stimulates germination
  • Delays Senescence

10
Gibberellins
  • Promotes seed and bud germination
  • Promotes stem elongation
  • Promotes leaf growth
  • Stimulates flowering and fruits
  • (with auxin)

11
Abscisic Acid
  • Inhibits growth (with gibberellins)
  • Closes stomata under water stress
  • Permits dormancy

12
Ethylene
  • Promotes fruit ripening
  • Controls Abscission
  • (with auxin)

13
Oligosaccharins
  • Triggers defense responses against pathogens
  • Regulates growth

14
Brassinosteroids
  • Required for normal growth and development

15
Signal-Transduction Pathways
  • A hormone binds to receptor and stimulates
    secondary messengers which Activates cell
    responses

16
Plant Movements
  • Phototropism
  • Gravitropism
  • Thigmotropism

17
Plant Movement
  • Rapid Leaf Movement
  • drop in turgor pressure within pulvini (at joints
    of the leaf)
  • sent by action potentials
  • Sleep Movements
  • cells on opposite sides of pulvinus control the
    movement

18
Daily and Seasonal Responses
  • Circadian Rhythm
  • Photoperiodism
  • controls flowering (short-day vs. long-day)
  • critical night length

19
Photoperiodic Control
20
Flowering Hormones
  • Experiment indicates the presence of some type of
    flowering hormone

21
Phytochromes
  • Function as photoreceptors / red (660nm) to far
    red (730nm)
  • Activates kinases (regulatory proteins)

22
Red vs. Far Red Response
23
Plant Responses to Environmental Stress
  • Water Deficit
  • Oxygen Deprivation
  • Salt Stress
  • Heat Stress
  • Cold Stress
  • Herbivores

24
Water Deficit
  • Slows Transpiration
  • stomata close
  • release of abscisic acid
  • Inhibits growth of young leaves
  • Change leaf shape
  • Deeper root growth

25
Oxygen Deprivation
  • Aerial roots
  • Production of air tubes

26
Salt Stress
  • Salt glands
  • Compatible solutes

27
Heat Stress
  • Heat-shock proteins

28
Cold Stress
  • Altering the lipid composition of their membranes
  • Changes in the solute composition of the cytosol

29
Responses to Herbivores
  • Produce Canavanine
  • Recruitment of predatory animals

30
Defense Against Pathogens
  • Gene-for-gene recognition

31
Defense Against Pathogens
  • Hypersensitive response (HR)
  • phytoalexins are released
  • PR proteins are released
  • Seal off infected area
  • Systemic acquired resistance (SAR)
  • Salicylic acid released due to death of cell
  • Activates a Signal Transduction Pathway
  • Activates SAR
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