Transcript 23-1 Specialized Tissues in Plants

Plant Structures
Roots, Stems, and Leaves
Chapter 23
23-1 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
23-1 Specialized Tissues in Plants
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Roots
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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
23-1 Specialized Tissues in Plants
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Stems
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Support for the plant
body
Carries nutrients
throughout plant
Defense system to
protect against predators
and infection
Few millimeters to 100
meters
23-1 Specialized Tissues in Plants
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Leaves
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Main photosynthetic
systems
Suseptable to extreme
drying
Sight of oxygen/carbon
dioxide intake and
release
23-1 Specialized Tissues in Plants
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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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23-1 Specialized Tissues in Plants
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Dermal Tissue
 Outer covering
 Single layer of cells
 Cuticle – waxy coating
 Trichomes – Spiny
projections on the
leaf
Roots have dermal tissue
 Root hairs
 Guard Cells
Change shape to open
and close stomata
23-1 Specialized Tissues in Plants
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Vascular Tissue
 Transport System
 TwoSubsystems
 Xylem
 Phloem
 Subsystems are used to carry fluids
throughout plant
23-1 Specialized Tissues in Plants
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Xylem – transport
water within plant.
Moves water upward
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Two types
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Seed plants
Angiosperms
Tracheid – long narrow
cells
Walls are connected to
neighboring cells
Will eventually die
Vessel Element – wider
that trachieds
23-1 Specialized Tissues in Plants
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Phloem – transport nutrients (food)
in the plant moving downward.
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Sieve Tube Elements
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Cells arranged end to end
Pump sugars and other foods
Companion Cells
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Surround sieve tube elements
Support phloem cells
23-1 Specialized Tissues in Plants
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Ground Tissue
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Cells between dermal
and vascular tissue
Parenchyma
 Thin cell walls, large
vacuoules
Collenchyma
 Strong, flexible cell
walls
Sclerenchyma
 Extremely thick, rigid
cell walls
23-1 Specialized Tissues in Plants
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Plant Growth
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Meristems – tissues
responsible for growth
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Apical Meristem
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Cells that divide to produce
increased length of stems
and roots.
Differentiation
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Undifferentiated cells
Cells will assume roles in
the plant
Flower Development
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Starts in the meristem
23-2 Roots
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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
23-2 Roots
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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
23-2 Roots
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Root Functions
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Anchor plant
Absorb water
Absorb nutrients
23-2 Roots
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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
23-2 Roots
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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
23-3 Stems
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Stem Functions
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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
23-3 Stems
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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
23-3 Stems
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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
23-3 Stems
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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
23-3 Stems
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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
23-3 Stems
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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
23-3 Roots
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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
23-4 Leaves
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Main sight 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
23-4 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
23-4 Leaves
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Transpiration
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Loss of water through its leaves
Replaced by water drawn into the leaf
23-4 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
23-5 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
23-5 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
23-5 Transport in Plants
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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
23-5 Transport in Plants
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Controlling
Transpiration
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Open the stomata –
increase water loss
Close the stomata –
decrease water loss
23-5 Transport in Plants
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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
23-5 Transport in Plants
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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