Transcript Chapter 35 Plant Structure

Plant Structures
Roots, Stems, and Leaves
Chapter 35
Heirarchy of Plant Structure
Specialized Tissues in Plants
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Plants are as successful
if not more successful
than animals
Seed plants have three
organ systems:
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Roots
Stems
Leaves
Linked together by
various means
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
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
Specialized Tissues in Plants
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Leaves
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Main photosynthetic
systems
Susceptible to extreme
drying
Sight of oxygen/carbon
dioxide intake and
release
Plant Cell Types
Collenchyma
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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Specialized Tissues in Plants
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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
Specialized Tissues in Plants
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Vascular Tissue System (Stele)
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Transport System
Subsystems
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Xylem
Phloem
Subsystems are used to carry fluids
throughout plant
Specialized Tissues in Plants
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Xylem
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Two types
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Tracheid – long narrow
and tapered cells
Walls are connected to
neighboring cells
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Seed plants
Angiosperms
Will eventually die
Vessel Element – wider
than tracheids
Specialized Tissues in Plants
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Phloem
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Sieve Tube Elements
 Cells arranged end to end
 Pump sugars and other foods
Companion Cells
 Surround sieve tube elements
 Support phloem cells
Specialized Tissues in Plants
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Ground Tissue
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Cells between dermal
and vascular tissue
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Contain parenchyma,
collenchyma, and
sclerenchyma cells
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Pith – ground tissue
internal to vascular
tissue
Cortex – ground
tissue external to
vascular tissue
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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Produce growth for
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
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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
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
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
Potassium
Magnesium
Calcium
Trace elements
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
Stems
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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
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
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Axillary, Apical
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
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
Stems
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Formation of Vascular
Cambium
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Xylem and phloem
bundles present initially
Secondary growth
initiates production of a
thin layer of cells
The vascular cambium
divides
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Produces new xylem and
phloem
Stems
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Formation of wood
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Wood – layers of xylem
Produced year after year
Results from the older xylem not conducting water –
heartwood
Becomes darker with age
Sapwood – surrounds heartwood
Stems
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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
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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
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 palisade level
Stomata – pores in the
underside of the leaf
Guard Cells – Surround
the stomata
Leaves
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Transpiration
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Loss of water through its leaves
Replaced by water drawn into the leaf
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
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
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
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
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
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