Transcript Plant Structure And Growth

Control Systems in Plants
Plant Hormones
Coordinates growth
 Coordinates development
 Coordinates responses to
environmental stimuli
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Plant Hormones
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Auxin (IAA)
Cytokinins
Gibberllins
Abscisic Acid
Ethylene
Oligogaccharins
Brassinosteroids
Auxins
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Stimulates stem elongation
Stimulates root growth
Stimulates differentiation and
branching
Stimulates development of fruit
Stimulates apical dominance
Stimulates phototropism and
gravitropism
Auxin Control
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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
Polar Transport
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Auxin is transported from
apex to shoot
Cell wall is acidic
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auxin ion picks up H+
diffuses across plasma
membrane
Cytosol is neutral
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auxon loses H+
uses energy to pump out H+
to maintain pH
leaves cell through carrier
proteins
Acid Growth Hypothesis
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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
Auxin Others
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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)
Cytokinins
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Stimulates root growth
Stimulates cell division and
differentiation (with auxins)
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more cytokinin - shoot buds develop
more auxin - roots develop
Stimulates germination
Delays Senescence
Gibberellins
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Promotes seed and bud germination
Promotes stem elongation
Promotes leaf growth
Stimulates flowering and fruits
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(with auxin)
Abscisic Acid
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Inhibits growth (with gibberellins)
Closes stomata under water stress
Permits dormancy
Ethylene
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Promotes fruit ripening
Controls Abscission
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(with auxin)
Oligosaccharins
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Triggers defense responses against
pathogens
Regulates growth
Brassinosteroids
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Required for normal growth and
development
Signal-Transduction Pathways
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A hormone binds to receptor and stimulates secondary
messengers which Activates cell responses
Plant Movements
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Phototropism
Gravitropism
Thigmotropism
Plant Movement
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Rapid Leaf Movement
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drop in turgor pressure within
pulvini (at joints of the leaf)
sent by action potentials
Sleep Movements
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cells on opposite sides of pulvinus
control the movement
Daily and Seasonal Responses
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Circadian Rhythm
Photoperiodism
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controls flowering (short-day vs. long-day)
critical night length
Photoperiodic Control
Flowering
Hormones
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Experiment
indicates the
presence of some
type of flowering
hormone
Phytochromes
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Function as photoreceptors / red (660nm) to far red (730nm)
Activates kinases (regulatory proteins)
Red vs. Far Red Response
Plant Responses to
Environmental Stress
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Water Deficit
Oxygen Deprivation
Salt Stress
Heat Stress
Cold Stress
Herbivores
Water Deficit
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Slows Transpiration
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stomata close
release of abscisic acid
Inhibits growth of young leaves
Change leaf shape
Deeper root growth
Oxygen Deprivation
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Aerial roots
Production of air tubes
Salt Stress
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Salt glands
Compatible solutes
Heat Stress
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Heat-shock proteins
Cold Stress
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Altering the lipid composition of
their membranes
Changes in the solute composition
of the cytosol
Responses to Herbivores
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Produce
Canavanine
Recruitment of
predatory
animals
Defense Against
Pathogens
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Gene-for-gene
recognition
Defense Against Pathogens
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Hypersensitive response (HR)
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phytoalexins are released
PR proteins are released
Seal off infected area
Systemic acquired resistance (SAR)
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Salicylic acid released due to death of cell
Activates a Signal Transduction Pathway
Activates SAR