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Plant Structures
Roots, Stems, and Leaves
Chapter 23
3 Types of Specialized Tissues in
Plants
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Plants are as successful
if not more successful
than animals
Seed plants have three
main structures:
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Roots
Stems
Leaves
Linked together by
various means
3 Types of Specialized Tissues in
Plants
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Roots
Absorbs water and nutrients
 Anchor plant to the ground
 Hold soil in place and
prevent erosion
 Protect from soil bacteria
 Transport water and nutrients
 Provide upright support
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3 Types of Specialized Tissues in
Plants
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Stems
Support for the plant body
 Carries nutrients throughout
plant
 Defense system to protect
against predators and
infection
 Few millimeters to 100
meters
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3 Types of Specialized Tissues in
Plants
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Leaves
Main photosynthetic
systems
 Susceptible to
extreme drying
 Site of
oxygen/carbon
dioxide intake and
release
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Plant Tissue Systems
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Exist within the
root, stems, and
leaves
Dermal tissue
 Vascular tissue
 Ground tissue
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Plant Tissue Systems: Dermal
Tissue
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Dermal Tissue
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Outer covering
Single layer of cells
Cuticle – waxy coating
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Roots have dermal
tissue
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Trichomes – Spiny
projections on the leaf
Root hairs
Guard Cells
Plant Tissue Systems: Vascular
Tissue
 Vascular Tissue
Transport System
 Subsystems
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Xylem
 Phloem
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Subsystems are used to carry fluids
throughout plant
Plant Tissue Systems: Vascular
Tissue
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Xylem
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Two types
Seed plants
 Angiosperms
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Tracheid – long narrow cells
 Walls are connected to
neighboring cells
 Will eventually die
 Vessel Element – wider that
trachieds
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Plant Tissue Systems: Vascular
Tissue
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Phloem
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Sieve Tube Elements
Cells arranged end to
end
 Pump sugars and
other foods
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Companion Cells
Surround sieve tube
elements
 Support phloem cells
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Specialized Tissues in Plants:
Ground Tissue
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Ground Tissue
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Cells between dermal and
vascular tissue
Parenchyma
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Collenchyma
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Thin cell walls, large
vacuoles
Strong, flexible cell walls
Sclerenchyma
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Extremely thick, rigid cell
walls
Plant Growth
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Meristems – tissues
responsible for growth
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Apical Meristem
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Produce growth increased
length
Differentiation
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Undifferentiated cells
Cells will assume roles in
the plant
Flower Development
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Starts in the meristem
Roots
Types of Roots
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Taproots
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Found in dicots
Long, thick root
Hickory and oak trees
Fibrous roots
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Found in monocots
No single root larger than any
other
Many thin roots
Root Structure
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Root Structure
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Outside layer
Epidermis
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Root hairs
Cortex
Central cylinder –
vascular system
Root Cap – cellular
production
Key role in
water/mineral transport
Root Functions
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Anchor plant
Absorb water
Absorb nutrients
Nutrient Uptake
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Plant Nutrient Uptake
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Soil type determines
plant type
Plant requirements
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Oxygen, CO2
Nitrogen
Phosphorus
Postassium
Magnesium
Calcium
Trace elements
Active Transport in Plants
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Root hairs use ATP
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Vascular Cylinder
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Pump minerals from soil
Causes water molecules
to follow by osmosis
Casparian Strip – water
retention
Root Pressure
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Forces water up into the
plant
Stems
Stem Structure
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Stem Structure
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Produce leaves,
branches, and flowers
Hold leaves up
Transport substance
between roots and leaves
Essential part of
transport system
Function in storage and
photosynthesis
Stem System
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Xylem and phloem – major
tubule systems
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Transport water and nutrients
Composed of three tissue
layers
Contain nodes – attachment
for leaves
Internodes – regions
between the nodes
Buds – undeveloped tissue
Stem Types
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Stem Types
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Monocot – vascular
bundles are scattered
throughout
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Distinct epidermis
Dicot – vascular tissue
arranged in a cylinder
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Pith – parenchyma cells
inside the ring
Stem Growth
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Stem Growth
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Primary growth – new
cells produced at the root
tips and shoots
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Increases the length
Secondary growth –
increase in stem width
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Vascular cambium –
produces tissue and
increases thickness
Cork cambium – produces
outer covering of stems
Vascular Cambium
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Formation of Vascular
Cambium
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Xylem and phloem
bundles present intially
Secondary growth
initiates production of a
thin layer
The vascular cambium
divides
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Produces new xylem and
phloem
Formation of Wood
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Formation of wood
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Wood – layers of exlem
Produced year after year
Results from the older xylem not conducting water –
heartwood
Becomes darker with age
Sapwood – surrounds heartwood
Formation of Wood
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Formation of Bark
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All the tissues outside
the vascular cambium
Consists of outermost
layers of dead cork
Water proof
Leaves
Leaves
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Main site of
photosynthesis
Consist of:
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Blade – thin flattened
section
Petiole – stalk that
attaches stem to blade
Covered by epidermis
and cuticle
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Create water proof
barrier
Function of Leaves
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Leaf Functions
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Photosynthesis – occurs
in the mesophyll
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Palisade mesophyll –
absorb light
Spongy mesophyll –
beneath palisede level
Stomata – pores in the
underside of the leaf
Guard Cells – Surround
the stomata
Transpiration
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Transpiration
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Loss of water through its leaves
Replaced by water drawn into the leaf
Function of Leaves
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Gas Exchange
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Take in CO2 and release
O2
Can also do the opposite
– How?
Gas exchange takes
place at the stomata
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Not open all the time
Stomata is controlled by
water pressure in guard
cells
Plant Transportation
Transport in Plants
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Water Transport
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Active transport and root
pressure
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Cause water to move from
soil to roots
Capillary action
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Combined with active
transport and root
pressure, moves materials
throughout the plant
Transport in Plants
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Capillary Transport
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Capillary transport
results from both
cohesive and adhesive
forces
Water molecules
attracted to one another
Water is also attracted to
the xylem tubes in the
plant
Causes water to move
from roots to the stem
and upward
Transpiration
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Transpiration
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Evaporation is the major
moving force
As water is lost, osmotic
pressure moves water out
of vascular tissue
This pulls water up from
the stem to the leaves
Affected by heat,
humidity, and wind
Transpiration
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Controlling
Transpiration
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Open the stomata –
increase water loss
Close the stomata –
decrease water loss
Transpiration
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Transpiration and
Wilting
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Osmotic pressure –
keeps plants semi-rigid
Wilting is a result of
high transpiration rates
Loss of water causes a
drop in osmotic pressure
Loss of rigidity
Conserves water
Nutrient Transportation
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Nutrient Transport
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Most nutrients are
pushed through plant
Nutrient movement takes
place in phloem
Source to Sink
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Source – any cell that
produces sugars
Sink – any cell where
sugars are used
Pressure-flow
Hypothesis