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8/7/2019 AP Bio PlantSecondaryGrowth& hormones(KFolgler)
1/20
AP Biology 2007-2008
Plant Growth
8/7/2019 AP Bio PlantSecondaryGrowth& hormones(KFolgler)
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8/7/2019 AP Bio PlantSecondaryGrowth& hormones(KFolgler)
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AP Biology
Growth in Plants
Specific regions of growth: meristems
stem cells: perpetually embryonic tissue
regenerate new cells
apical shoot meristem growth in length
primary growth
apical root meristem
growth in length primary growth
lateral meristem
growth in girth
secondary growth
8/7/2019 AP Bio PlantSecondaryGrowth& hormones(KFolgler)
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AP Biology
Apical meristems
shoot root
8/7/2019 AP Bio PlantSecondaryGrowth& hormones(KFolgler)
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AP Biology
Root structure & growth
protecting the meristem
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8/7/2019 AP Bio PlantSecondaryGrowth& hormones(KFolgler)
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AP Biology
Woody plants grow inheight from tip
primary growth
apical meristem
Woody plants grow indiameterfrom sides
secondary growth
lateral meristems vascular cambium
makes 2 phloem & 2 xylem
cork cambium
makes bark
Growth in woody plants
Primaryphloem Primary
xylemSecondaryphloem
Secondaryxylem
Annualgrowthlayers
Lateralmeristems
Primaryxylem
Primaryphloem
Bark
Epidermis
8/7/2019 AP Bio PlantSecondaryGrowth& hormones(KFolgler)
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AP Biology
Secondary growth
Secondary growth
growth in diameter thickens & strengthens older part of tree
cork cambium makes bark
growing ring around tree
vascular cambium makes xylem & phloem
growing ring around tree
8/7/2019 AP Bio PlantSecondaryGrowth& hormones(KFolgler)
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AP Biology
Vascular cambium
last years xylem
early
late
phloem
bark
Phloem produced to the outside
Xylem produced to the inside
corkcambium
vascularcambium
xylem
Why are early& late growth
different?
8/7/2019 AP Bio PlantSecondaryGrowth& hormones(KFolgler)
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AP Biology
Woody stem cork cambium
vascular cambium
xylem
early
late
phloem bark
How old is
this tree?
1
2
3
8/7/2019 AP Bio PlantSecondaryGrowth& hormones(KFolgler)
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AP Biology
Tree trunk anatomy
tree girdling
What does girdling
do to a tree?
Aaaargh!Murderer!Arborcide!
8/7/2019 AP Bio PlantSecondaryGrowth& hormones(KFolgler)
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AP Biology
Where will the carving be in 50 years?
8/7/2019 AP Bio PlantSecondaryGrowth& hormones(KFolgler)
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AP Biology
Plant hormones
auxin
gibberellins
abscisic acid
ethylene
and more
8/7/2019 AP Bio PlantSecondaryGrowth& hormones(KFolgler)
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AP Biology
Auxin (IAA)
Effects
controls cell division
& differentiation
phototropism growth towards light
asymmetrical distribution of auxin
cells on darker side elongate faster
than cells on brighter side
apical dominance
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8/7/2019 AP Bio PlantSecondaryGrowth& hormones(KFolgler)
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AP Biology
Abscisic acid (ABA)
Effects
slows growth
seed dormancy
high concentrations ofabscisic acid germination only after ABA is inactivated or
leeched out
survival value:
seed will germinate onlyunder optimal conditions
light, temperature, moisture
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AP Biology
Ethylene
Hormone gas released by plant cells
Effects
fruit ripening
leaf drop
like in Autumn
apoptosis
One bad applespoils the
whole bunch
8/7/2019 AP Bio PlantSecondaryGrowth& hormones(KFolgler)
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AP Biology
Fruit ripening
Adaptation
hard, tart fruit protectsdeveloping seed from herbivores
ripe, sweet, soft fruit attracts
animals to disperse seed Mechanism
triggers ripening process breakdown of cell wall
softening
conversion of starch to sugar
sweetening
positive feedback system ethylene triggers ripening
ripening stimulates more ethylene production
8/7/2019 AP Bio PlantSecondaryGrowth& hormones(KFolgler)
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AP Biology
Apoptosis in plantsWhat is theevolutionary
advantage of
loss of leaves
in autumn?
Many events in plantsinvolve apoptosis
response to hormones
ethylene
auxin
death of annual plant after
flowering
senescence
differentiation of xylemvessels
loss of cytoplasm
shedding of autumn leaves
8/7/2019 AP Bio PlantSecondaryGrowth& hormones(KFolgler)
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AP Biology 2007-2008
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