Download Chapter 35_Plant Anatomy and Growth

AP Biology – Chapter 35
Plant Anatomy
AP Biology
2006-2007
Overview
  Plasticity – plants undergo extreme developmental
changes
 
Compensate for inability to move
  Plant form is controlled by environmental and
genetic factors
  Species of plants accumulate adaptations in
morphology – vary little among plants within the
species
 
Example – cacti leaves
  Effect of environment is greater in plants
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Plant Anatomy
  Organs composed of different tissues, tissues
composed of different cell types
  Tissue – group of cells with common structure
and function
  Organ – consists of several types of tissues
that together carry out particular functions
  3 basic plant organs:
1. 
2. 
3. 
Roots
Stems
Leaves
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AP Biology – Chapter 35
Basic plant anatomy 1
  Plants draw
resources from
two different
environments:
  Below ground –
root system
  Above ground –
shoot system
  Root system
 
 
root tip
root hairs
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Roots
  Roots anchor plant in soil, absorb
minerals & water, & store food
 
fibrous roots (1)
  mat of thin roots that spread out
  monocots
 
tap roots (2)
  1 large vertical root
  also produces many small lateral,
or branch roots
  dicots
 
root hairs (3)
2
  increase absorptive
surface area
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Apical bud
Basic plant anatomy 2
  root
node
internode
root tip
  root hairs
 
  shoot (stem)
 
Nodes – point where
leaves are attached
  internodes
 
Axillary bud
buds
  terminal or apical buds
  axillary buds
  flower buds & flowers
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Modified shoots
stolons (strawberries)
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rhizome (ginger)
tuber (potato)
bulb (onion)
Basic plant anatomy 3
  root
 
 
root tip
root hairs
  shoot (stem)
 
nodes
 
buds
  internodes
  terminal or apical buds
  axillary buds
  flower buds & flowers
  leaves
 
 
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mesophyll tissue
veins (vascular bundles)
Leaves
  Function of leaves
 
photosynthesis
  energy production
  CHO production
gas exchange
  transpiration
 
simple vs. compound
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Modified leaves
tendrils (peas)
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succulent leaves
spines (cacti)
colored leaves (poinsetta)
Interdependent systems
  Both systems
depend on the
other
roots depend on
sugars produced
by photosynthetic
leaves
  shoots depend on
water & minerals
absorbed from the
soil by roots
sugars
 
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water &
minerals
Plant TISSUES
  Dermal
 
 
epidermis (“skin” of plant)
single layer of tightly packed
cells that covers
& protects plant
  Vascular
 
 
 
 
transport system in
shoots & roots
Xylem brings water and
minerals upward (roots to
shoots)
Phloem transports sugars
made in the leaves to the
roots
Vascular bundles
  Ground
 
 
bulk of plant tissue
photosynthetic mesophyll,
storage
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AP Biology – Chapter 35
Plant CELL types in plant tissues
  Parenchyma
“typical” plant cells = least specialized
photosynthetic cells, storage cells
  tissue of leaves, stem, fruit, storage roots
 
 
  Collenchyma
 
 
unevenly thickened primary walls
support
  Sclerenchyma
very thick, “woody” secondary walls
support
  rigid cells that can’t elongate
  dead at functional maturity
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 
 
Parenchyma
  Parenchyma cells are unspecialized, thin, flexible &
carry out many metabolic functions
 
all other cell types in plants develop from parenchyma
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Collenchyma
  Collenchyma cells have thicker primary walls &
provide support
 
 
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help support without restraining growth
remain alive in maturity
the strings in celery stalks
are collenchyma
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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
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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
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Phloem: food-conducting cells
  sieve tube elements & companion cells
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AP Biology – Chapter 35
Phloem: food-conducting cells
  carry sugars & nutrients throughout plant
sieve tube
companion cell
sieve plate
plasmodesmata
living cells
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Phloem
Aaaah…
Structure–Function
again!
  Living cells at functional maturity
 
cell membrane, cytoplasm
 
lose their nucleus, ribosomes & vacuole
  control of diffusion
  more room for specialized transport of
liquid food (sucrose)
  Cells
 
sieve tubes
  sieve plates — end walls — have pores to facilitate
flow of fluid between cells
 
companion cells
  nucleated cells connected to the sieve-tube
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  help sieve tubes
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AP Biology – Chapter 35
Putting it all together
  Obtaining raw materials
 
sunlight
 
CO2
 
H 2O
 
nutrients
  leaves = solar collectors
  stomates = gas exchange
  uptake from roots
  uptake from roots
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Vascular tissue in stems
dicot
trees & shrubs
monocot
grasses & lilies
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collect annual rings
Phloem
sieve plate
sieve
tubes
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AP Biology – Chapter 35
Plant Growth
AP Biology
2007-2008
Plant Growth
  Indeterminate growth
Major difference between plants and
animals
  Plant growth is not limited to an embryonic
period
  Plant growth occurs throughout the plant
life
 
  Determinate growth
Most animals and certain plant organs –
flowers and leaves
  Ceasing to grow after they reach a certain
size
 
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Growth in Plants
  Specific regions of growth: meristems
 
 
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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
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AP Biology – Chapter 35
Apical meristems
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shoot
root
Root Structure and Growth
  Root cap – the tip of a root is covered by a root cap
 
 
Protects the apical meristem as the root pushes
through the soil during primary growth
Secretes slime to lubricate soil
  Zone of cell division
 
Where new root cells are produced
  Zone of cell elongation
 
Where cells elongate – responsible for pushing the
root tip ahead
  Zone of maturation
 
Cells differentiate and become functionally mature
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Root structure & growth
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protecting the meristem
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AP Biology – Chapter 35
Vascular tissue in roots: dicot
xylem
phloem
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Vascular tissue in roots: monocot
xylem
phloem
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Shoot growth
  Apical bud & primary
growth of shoot
 
 
region of stem growth
axillary buds
  “waiting in the wings”
protecting the meristem
Young leaf
primordium
Apical meristem
Older leaf
primordium
Lateral bud
primordium
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Vascular tissue
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AP Biology – Chapter 35
Tissue Organization of Leaves
  Leaf epidermis
First line of defense against physical damage
Waxy cuticle serves as a barrier to water loss
  Stomata
  Tiny pores allow for gas exchange between
surrounding air and photosynthetic cells inside the
leaf
  Regulates CO2 uptake for photosynthesis
  Mesophyll
  Ground tissue of the leaf; found between the upper
and lower epidermal layers
  Specialized for photosynthesis
 
 
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Putting it all together
  Obtaining raw materials
 
sunlight
 
CO2
 
H 2O
 
nutrients
  leaves = solar collectors
  stomates = gas exchange
  uptake from roots
  uptake from roots
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AP Biology – Chapter 35
Secondary Growth in
woody plants
Primary
xylem
Primary
phloem
  Woody plants grow in
height from tip
 
 
Epidermis
Lateral
meristems
primary growth
apical meristem
  Woody plants grow in
diameter from sides
Primary
phloem
secondary growth
  lateral meristems
 
Secondary
phloem
Primary
xylem
Secondary
xylem
  vascular cambium
  makes 2° phloem & 2° xylem
  cork cambium
  makes bark
Annual
growth
layers
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Bark
Cork cambium
Secondary growth
Vascular cambium
  Secondary growth
 
growth in diameter
 
cork cambium makes bark
 
vascular cambium makes xylem & phloem
  thickens & strengthens older part of tree
  growing ring around tree
  growing ring around tree
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Vascular cambium
 Phloem produced to the outside
 Xylem produced to the inside
bark
cork
cambium
phloem
xylem
vascular
cambium
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late
early
last year’s xylem
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AP Biology – Chapter 35
cork cambium
Woody stem
vascular cambium
late
early
3
2
1
xylem
phloem
bark
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Secondary Growth
  Heartwood
 
 
 
as a tree ages, older layers of secondary xylem
no longer transport water and minders
Closer to the center of a stem or root
  Sapwood
 
 
 
outer layers
continue to transport xylem sap
*why a large tree can survive even if the center of the trunk is
hollow
  Cork cambium
 
Thick covering for stems and roots that replaces the epidermis
  Periderm – cork + cork cambium
  Bark – refers to all tissues external to the vascular cambium
 
Consists of secondary phloem, cork cambium and cork
  Secondary growth enables the xylem to transport more sap
each year – supplying an increase in the number of leaves
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Tree trunk anatomy
tree girdling
What does girdling
do
to a tree?
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Where will the carving be in 50 years?
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