Plant Structures
Plant Structures
Roots, Stems, and Leaves
Roots, Stems, and Leaves
Chapter 23
Chapter 23
Plant Structures
Plant Structures
Roots, Stems, and Leaves
Roots, Stems, and Leaves
Chapter 23
Chapter 23
23-1 Specialized Tissues
23-1 Specialized Tissues
in Plants
in Plants
Plants are as
Plants are as
successful if not
successful if not
more successful than
more successful than
animals
animals
Seed plants have
Seed plants have
three main
three main
structures:
structures:
Roots
Roots
Stems
Stems
Leaves
Leaves
Linked together by
Linked together by
various means
various means
23-1 Specialized Tissues
23-1 Specialized Tissues
in Plants
in Plants
Roots
Roots
Absorbs water and
Absorbs water and
nutrients
nutrients
Anchor plant to the
Anchor plant to the
ground
ground
Hold soil in place and
Hold soil in place and
prevent erosion
prevent erosion
Protect from soil
Protect from soil
bacteria
bacteria
Transport water and
Transport water and
nutrients
nutrients
Provide upright
Provide upright
support
support
23-1 Specialized Tissues
23-1 Specialized Tissues
in Plants
in Plants
Stems
Stems
Support for the
Support for the
plant body
plant body
Carries nutrients
Carries nutrients
throughout plant
throughout plant
Defense system to
Defense system to
protect against
protect against
predators and
predators and
infection
infection
Few millimeters to
Few millimeters to
100 meters
100 meters
23-1 Specialized Tissues
23-1 Specialized Tissues
in Plants
in Plants
Leaves
Leaves
Main
Main
photosynthetic
photosynthetic
systems
systems
Suseptable to
Suseptable to
extreme drying
extreme drying
Sight of
Sight of
oxygen/carbon
oxygen/carbon
dioxide intake and
dioxide intake and
release
release
23-1 Specialized Tissues
23-1 Specialized Tissues
in Plants
in Plants
Plant tissue
Plant tissue
systems
systems
Exist within the
Exist within the
root, stems,
root, stems,
and leaves
and leaves
Dermal tissue
Dermal tissue
Vascular tissue
Vascular tissue
Ground tissue
Ground tissue
23-1 Specialized Tissues
23-1 Specialized Tissues
in Plants
in Plants
Dermal Tissue
Dermal Tissue
Outer covering
Outer covering
Single layer of cells
Single layer of cells
Cuticle
Cuticle
– waxy
– waxy
coating
coating
Trichomes
Trichomes
–
–
Spiny
Spiny
projections on the leaf
projections on the leaf
Roots have dermal
Roots have dermal
tissue
tissue
Root hairs
Root hairs
Guard Cells
Guard Cells
23-1 Specialized Tissues
23-1 Specialized Tissues
in Plants
in Plants
Vascular Tissue
Vascular Tissue
Transport System
Transport System
Subsystems
Subsystems
Xylem
Xylem
Phloem
Phloem
Subsystems are used to carry
Subsystems are used to carry
fluids throughout plant
fluids throughout plant
23-1 Specialized Tissues
23-1 Specialized Tissues
in Plants
in Plants
Xylem
Xylem
Two types
Two types
Seed plants
Seed plants
Angiosperms
Angiosperms
Tracheid
Tracheid
– long
– long
narrow cells
narrow cells
Walls are connected
Walls are connected
to neighboring cells
to neighboring cells
Will eventually die
Will eventually die
Vessel Element
Vessel Element
–
–
wider that trachieds
wider that trachieds
23-1 Specialized Tissues
23-1 Specialized Tissues
in Plants
in Plants
Phloem
Phloem
Sieve Tube Elements
Sieve Tube Elements
Cells arranged end to end
Cells arranged end to end
Pump sugars and other foods
Pump sugars and other foods
Companion Cells
Companion Cells
Surround sieve tube elements
Surround sieve tube elements
Support phloem cells
Support phloem cells
23-1 Specialized Tissues
23-1 Specialized Tissues
in Plants
in Plants
Ground Tissue
Ground Tissue
Cells between dermal
Cells between dermal
and vascular tissue
and vascular tissue
Parenchyma
Parenchyma
Thin cell walls, large
Thin cell walls, large
vacuoules
vacuoules
Collenchyma
Collenchyma
Strong, flexible cell
Strong, flexible cell
walls
walls
Sclerenchyma
Sclerenchyma
Extremely thick, rigid
Extremely thick, rigid
cell walls
cell walls
23-1 Specialized Tissues
23-1 Specialized Tissues
in Plants
in Plants
Plant Growth
Plant Growth
Meristems
Meristems
– tissues
– tissues
responsible for growth
responsible for growth
Undifferentiated cells
Undifferentiated cells
Apical Meristem
Apical Meristem
Produce growth
Produce growth
increased length
increased length
Differentiation
Differentiation
Cells will assume roles
Cells will assume roles
in the plant
in the plant
Flower Development
Flower Development
Starts in the meristem
Starts in the meristem
23-2 Roots
23-2 Roots
Types of Roots
Types of Roots
Taproots
Taproots
Found in dicots
Found in dicots
Long, thick root
Long, thick root
Hickory and oak trees
Hickory and oak trees
Fibrous roots
Fibrous roots
Found in monocots
Found in monocots
No single root larger than any other
No single root larger than any other
Many thin roots
Many thin roots
23-2 Roots
23-2 Roots
Root Structure
Root Structure
Outside layer
Outside layer
Epidermis
Epidermis
Root hairs
Root hairs
Cortex
Cortex
Central cylinder –
Central cylinder –
vascular system
vascular system
Root Cap – cellular
Root Cap – cellular
production
production
Key role in
Key role in
water/mineral
water/mineral
transport
transport
23-2 Roots
23-2 Roots
Root Functions
Root Functions
Anchor plant
Anchor plant
Absorb water
Absorb water
Absorb nutrients
Absorb nutrients
23-2 Roots
23-2 Roots
Plant Nutrient
Plant Nutrient
Uptake
Uptake
Soil type determines
Soil type determines
plant type
plant type
Plant requirements
Plant requirements
Oxygen, CO
Oxygen, CO
2
2
Nitrogen
Nitrogen
Phosphorus
Phosphorus
Postassium
Postassium
Magnesium
Magnesium
Calcium
Calcium
Trace elements
Trace elements
23-2 Roots
23-2 Roots
Active Transport in
Active Transport in
Plants
Plants
Root hairs use ATP
Root hairs use ATP
Pump minerals from
Pump minerals from
soil
soil
Causes water
Causes water
molecules to follow by
molecules to follow by
osmosis
osmosis
Vascular Cylinder
Vascular Cylinder
Casparian Strip –
Casparian Strip –
water retention
water retention
Root Pressure
Root Pressure
Forces water up into
Forces water up into
the plant
the plant
23-3 Stems
23-3 Stems
Stem Structure
Stem Structure
Produce leaves,
Produce leaves,
branches, and flowers
branches, and flowers
Hold leaves up
Hold leaves up
Transport substance
Transport substance
between roots and
between roots and
leaves
leaves
Essential part of
Essential part of
transport system
transport system
Function in storage
Function in storage
and photosynthesis
and photosynthesis
23-3 Stems
23-3 Stems
Xylem and phloem –
Xylem and phloem –
major tubule systems
major tubule systems
Transport water and
Transport water and
nutrients
nutrients
Composed of three
Composed of three
tissue layers
tissue layers
Contain
Contain
nodes
nodes
–
–
attachment for leaves
attachment for leaves
Internodes
Internodes
– regions
– regions
between the nodes
between the nodes
Buds
Buds
– undeveloped
– undeveloped
tissue
tissue
23-3 Stems
23-3 Stems
Stem Types
Stem Types
Monocot
Monocot
–
–
vascular bundles
vascular bundles
are scattered
are scattered
throughout
throughout
Distinct epidermis
Distinct epidermis
Dicot
Dicot
– vascular
– vascular
tissue arranged in a
tissue arranged in a
cylinder
cylinder
Pith
Pith
– parenchyma
– parenchyma
cells inside the ring
cells inside the ring
23-3 Stems
23-3 Stems
Stem Growth
Stem Growth
Primary growth – new
Primary growth – new
cells produced at the
cells produced at the
root tips and shoots
root tips and shoots
Increases the length
Increases the length
Secondary growth –
Secondary growth –
increase in stem width
increase in stem width
Vascular cambium –
Vascular cambium –
produces tissue and
produces tissue and
increases thickness
increases thickness
Cork cambium –
Cork cambium –
produces outer
produces outer
covering of stems
covering of stems
23-3 Stems
23-3 Stems
Formation of
Formation of
Vascular Cambium
Vascular Cambium
Xylem and phloem
Xylem and phloem
bundles present
bundles present
intially
intially
Secondary growth
Secondary growth
initiates production
initiates production
of a thin layer
of a thin layer
The vascular
The vascular
cambium divides
cambium divides
Produces new xylem
Produces new xylem
and phloem
and phloem
23-3 Stems
23-3 Stems
Formation of wood
Formation of wood
Wood – layers of exlem
Wood – layers of exlem
Produced year after year
Produced year after year
Results from the older xylem not conducting water –
Results from the older xylem not conducting water –
heartwood
heartwood
Becomes darker with age
Becomes darker with age
Sapwood
Sapwood
– surrounds heartwood
– surrounds heartwood
23-3 Roots
23-3 Roots
Formation of Bark
Formation of Bark
All the tissues
All the tissues
outside the
outside the
vascular cambium
vascular cambium
Consists of
Consists of
outermost layers of
outermost layers of
dead cork
dead cork
Water proof
Water proof
23-4 Leaves
23-4 Leaves
Main sight of
Main sight of
photosynthesis
photosynthesis
Consist of:
Consist of:
Blade – thin flattened
Blade – thin flattened
section
section
Petiole – stalk that
Petiole – stalk that
attaches stem to blade
attaches stem to blade
Covered by
Covered by
epidermis and cuticle
epidermis and cuticle
Create water proof
Create water proof
barrier
barrier
23-4 Leaves
23-4 Leaves
Leaf Functions
Leaf Functions
Photosynthesis –
Photosynthesis –
occurs in the
occurs in the
mesophyll
mesophyll
Palisade mesophyll –
Palisade mesophyll –
absorb light
absorb light
Spongy mesophyll –
Spongy mesophyll –
beneath palisede level
beneath palisede level
Stomata – pores in the
Stomata – pores in the
underside of the leaf
underside of the leaf
Guard Cells
Guard Cells
–
–
Surround the stomata
Surround the stomata
23-4 Leaves
23-4 Leaves
Transpiration
Transpiration
Loss of water through its leaves
Loss of water through its leaves
Replaced by water drawn into the leaf
Replaced by water drawn into the leaf
23-4 Leaves
23-4 Leaves
Gas Exchange
Gas Exchange
Take in CO
Take in CO
2
2
and
and
release O
release O
2
2
Can also do the
Can also do the
opposite – How?
opposite – How?
Gas exchange takes
Gas exchange takes
place at the stomata
place at the stomata
Not open all the time
Not open all the time
Stomata is controlled
Stomata is controlled
by water pressure in
by water pressure in
guard cells
guard cells
23-5 Transport in Plants
23-5 Transport in Plants
Water Transport
Water Transport
Active transport
Active transport
and root pressure
and root pressure
Cause water to
Cause water to
move from soil to
move from soil to
roots
roots
Capillary action
Capillary action
Combined with
Combined with
active transport and
active transport and
root pressure,
root pressure,
moves materials
moves materials
throughout the plant
throughout the plant
23-5 Transport in Plants
23-5 Transport in Plants
Capillary Transport
Capillary Transport
Capillary transport
Capillary transport
results from both
results from both
cohesive and
cohesive and
adhesive forces
adhesive forces
Water molecules
Water molecules
attracted to one
attracted to one
another
another
Water is also
Water is also
attracted to the xylem
attracted to the xylem
tubes in the plant
tubes in the plant
Causes water to move
Causes water to move
from roots to the
from roots to the
stem and upward
stem and upward
23-5 Transport in Plants
23-5 Transport in Plants
Transpiration
Transpiration
Evaporation is the
Evaporation is the
major moving force
major moving force
As water is lost,
As water is lost,
osmotic pressure
osmotic pressure
moves water out of
moves water out of
vascular tissue
vascular tissue
This pulls water up
This pulls water up
from the stem to the
from the stem to the
leaves
leaves
Affected by heat,
Affected by heat,
humidity, and wind
humidity, and wind
23-5 Transport in Plants
23-5 Transport in Plants
Controlling
Controlling
Transpiration
Transpiration
Open the stomata –
Open the stomata –
increase water loss
increase water loss
Close the stomata –
Close the stomata –
decrease water loss
decrease water loss
23-5 Transport in Plants
23-5 Transport in Plants
Transpiration and
Transpiration and
Wilting
Wilting
Osmotic pressure –
Osmotic pressure –
keeps plants semi-rigid
keeps plants semi-rigid
Wilting is a result of
Wilting is a result of
high transpiration
high transpiration
rates
rates
Loss of water causes a
Loss of water causes a
drop in osmotic
drop in osmotic
pressure
pressure
Loss of rigidity
Loss of rigidity
Conserves water
Conserves water
23-5 Transport in Plants
23-5 Transport in Plants
Nutrient Transport
Nutrient Transport
Most nutrients are
Most nutrients are
pushed
pushed
through plant
through plant
Nutrient movement
Nutrient movement
takes place in phloem
takes place in phloem
Source to Sink
Source to Sink
Source – any cell that
Source – any cell that
produces sugars
produces sugars
Sink – any cell where
Sink – any cell where
sugars are used
sugars are used
Pressure-flow
Pressure-flow
Hypothesis
Hypothesis