Transcript Woody plants grow in diameter from sides secondary growth

Plant Growth
Growth in Animals
 Animals grow throughout the whole
organism

many regions & tissues at different rates
Growth in Plants
 Specific regions of growth: _____________
stem cells: perpetually embryonic tissue
 regenerate new cells

 ___________________
 growth in length
 primary growth
 ___________________
 growth in length
 primary growth
 ___________________
 growth in girth (width)
 secondary growth
Apical meristems
shoot
shoot
Root structure & growth
protecting the meristem
Shoot growth
 Apical bud & primary
growth of shoot
region of stem growth
 __________________

 “waiting in the wings”
protecting the meristem
Young leaf
primordium
Apical meristem
Older leaf
primordium
Lateral bud
primordium
Vascular tissue
Primary
xylem
Growth in woody plants
Primary
phloem
 Woody plants grow in
Epidermis
height from tip


Lateral
meristems
primary growth
______________________
 Woody plants grow in
diameter from sides


Primary
phloem
secondary growth
______________________
Secondary
phloem
Secondary
Primary xylem
xylem
 _____________________
 makes 2° phloem & 2° xylem
 _____________________
 makes bark
Annual
growth
layers
Bark
Secondary growth
 Secondary growth

growth in diameter
 thickens & strengthens older part of tree

____________________________________
 growing ring around tree

____________________________________
 growing ring around tree
Vascular cambium
Why are early
& late growth
different?
 Phloem produced to the outside
 Xylem produced to the inside
bark
cork
cambium
phloem
phloem
vascular
cambium
late
early
last year’s xylem
cork cambium
Woody stem
How old is
this tree?
vascular cambium
late
early
3
2
1
xylem
phloem
bark
Tree trunk anatomy
tree girdling
What does girdling
do to a tree?
Aaaargh!
Murderer!
Arborcide!
Tree trunk anatomy
tree girdling
What does girdling
do to a tree?
Aaaargh!
Murderer!
Arborcide!
Where will the carving be in 50 years?
Plant hormones
 __________________
 __________________
 __________________
 __________________
 and more…
Auxin (IAA)
 Effects
controls cell division
& differentiation
 __________________

 growth towards light
 asymmetrical distribution of auxin
 cells on darker side elongate faster
than cells on brighter side

__________________
Gibberellins
 Family of hormones

over 100 different gibberellins identified
 Effects
stem elongation
 ____________________
 ____________________

plump grapes in grocery
stores have been treated
with gibberellin hormones
while on the vine
Abscisic acid (ABA)
 Effects
____________________
 ____________________

 high concentrations of abscisic acid
 germination only after ABA is inactivated or
leeched out
 survival value:
seed will germinate only
under optimal conditions
 light, temperature, moisture
Ethylene
 Hormone gas released by plant cells
 Effects
____________________
 ____________________

 like in Autumn
 apoptosis
One bad apple
spoils the
whole bunch…
Fruit ripening
 Adaptation


hard, tart fruit protects
developing 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
 clusters of fruit ripen together
Apoptosis in plants
 Many events in plants
involve apoptosis

response to hormones
 ethylene
 auxin

death of annual plant after
flowering
 senescence

differentiation of xylem
vessels
 loss of cytoplasm

shedding of autumn leaves
What is the
evolutionary
advantage of
loss of leaves
in autumn?
Don’t take this lying down…
Ask Questions!!
2007-2008
Apical meristems
shoot
shoot
Root structure & growth
protecting the meristem
Shoot growth
 Apical bud & primary
growth of shoot
region of stem growth
 __________________

 “waiting in the wings”
protecting the meristem
Young leaf
primordium
Apical meristem
Older leaf
primordium
Lateral bud
primordium
Vascular tissue
Primary
xylem
Growth in woody plants
Primary
phloem
 Woody plants grow in
Epidermis
height from tip


Lateral
meristems
primary growth
______________________
 Woody plants grow in
diameter from sides


Primary
phloem
secondary growth
______________________
Secondary
phloem
Secondary
Primary xylem
xylem
 _____________________
 makes 2° phloem & 2° xylem
 _____________________
 makes bark
Annual
growth
layers
Bark
Vascular cambium
Why are early
& late growth
different?
 Phloem produced to the outside
 Xylem produced to the inside
bark
cork
cambium
phloem
phloem
vascular
cambium
late
early
last year’s xylem
cork cambium
Woody stem
How old is
this tree?
vascular cambium
late
early
3
2
1
xylem
phloem
bark
Basic plant anatomy 1
Leaves
 Function of leaves

photosynthesis
 energy production
 CHO production
gas exchange
 transpiration

simple vs. compound
Parenchyma
 Parenchyma cells are unspecialized, thin, flexible &
carry out many metabolic functions

all other cell types in plants develop from parenchyma
Collenchyma
 Collenchyma cells have thicker primary walls &
provide support


help support without restraining growth
remain alive in maturity
the strings in celery stalks
are collenchyma
Sclerenchyma
 Thick, rigid cell wall



lignin (wood)
cannot elongate
mostly dead at maturity
 Cells for support



xylem vessels
xylem tracheids
fibers
 rope fibers

sclereids
 nutshells
 seed coats
 grittiness in pears
vessel elements
 Xylem

vessel
element

Vascular tissue
move water & minerals up from roots
dead cells at functional maturity
 only cell walls remain
 need empty pipes to efficiently move H2O
 transpirational pull
dead cells
Aaaah…
Structure–Function
again!
tracheids
Phloem: food-conducting cells
 carry sugars & nutrients throughout plant
sieve tube
companion cell
sieve plate
plasmodesmata
living cells
Phloem: food-conducting cells
 sieve tube elements & companion cells
Vascular tissue in stems
dicot
trees & shrubs
collect annual rings
monocot
grasses & lilies
Vascular tissue in roots: dicot
phloem
xylem
Vascular tissue in roots: monocot
xylem
phloem
Flower
 Modified shoot with 4 rings
of modified leaves
sepals Stamen
 petals
 stamens

Stigma
Style
Ovary
Anther
Carpel
Filament
 male

carpel
 female
sepals
petals
stamens
Petal
Ovule
Sepal
adaptations through mutations
carpel
What is a Cotyledon?
 Cotyledon: seed leaf in the embryo of an
angiosperm that hold food for the
developing plant

May form a leaf after germination