Specialized Tissues in Plants

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Specialized Tissues in Plants

• How is the plant kingdom different from other
  kingdoms?
• 4/13/07

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Principal Organs

• Roots? absorb water and dissolved nutrients, hold
  plant upright
• Stems? support plant body and transport nutrients
• Leaves? carry out photosynthesis and protect
  against water loss

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Tissue Systems

• 3 tissue systems
• Dermal tissue? outermost layer
• Vascular tissue? transports nutrients throughout
  plant
• Ground tissue? everything else
• Meristematic tissue? tips of shoots and roots
  responsible for growth

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Dermal Tissue

• Outermost covering of a plant
• Single layer of cells
• Cuticle? thick waxy layer covering outer surface
  of epidermal cells
• Roots have root hair
• Leaves contain guard cells

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Vascular Tissue

• Transports water and nutrient throughout plant
• 2 types
• Xylem
• Phloem

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Xylem

• Water conducting tissue consisting of tracheids
  and vessel
• Tracheids? long narrow cells with walls that are
  impermeable to waterhave holes in the walls that
  connect neighboring cells
• Used to get water and minerals up through the
  plant

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Phloem

• Food conducting tissue consisting of sieve tube
  elements and companion cells
• Sieve tube elements? arrange end to end. Have
  small holes at the end and when they die create a
  pipeline for nutrients to travel
• Companion cells? surround sieve tube
  elementssupport phloem cells and aid in movement
  of substances out of streams
• Carries food from leaves to roots or stems

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Ground Tissue

• Between dermal and vascular tissues
• Parenchyma? thin cell walls large central
  vacuoles, packed with chloroplasts
• Collenchyma? strong flexible cell walls that help
  support larger plants
• Sclerenchyma? Cells have extremely thick, rigid
  cell walls that make ground tissue tough and
  strong

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Parenchyma
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Parenchyma
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Collenchyma
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Sclerenchyma
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Meristematic Tissue

• Plants grow as long as they live
• Meristematic tissue is the only tissue that
  produces new cells
• Apical meristem? group of undifferentiated cells
  that divide to produce increased length of stems
  and roots

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Structure and Growth
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Roots

• 2 types
• Taproots (dicots)
• One large primary root with small secondary roots
  
• Fibrous roots (monocots)
• Branch off in equal sizes

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Types of roots
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Root Structure

• Three layers of tissue in a root
• Epidermis outer layer
• Root hairs increase surface area
• Vascular tissue central cylinder
• Ground tissue tissue that lies between the
  others

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Root Structure cont

• Root cap protects meristematic tissue
• Cortex? spongy layer inside epidermis
• Endodermis? encloses the vascular tissue in the
  center

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Root Functions

• Anchor plant to ground
• Absorb water and nutrients from soil
• Endodermis surrounded by waterproof strip called
  Casparian strip
• Once water/minerals in cant get out
• Puts pressure on water causing it to rise inside
  xylem b/c no place to go.

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Root function
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Stems

• 3 important functions
• Produce leaves, branches, and flowers
• Hold leaves up in the sunlight
• Transport substances between roots and leaves
• 3 things stems have
• Nodes? leaf is attached
• Internodes? regions between nodes
• Buds? underdeveloped tissue that can produce new
  stems and leaves

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Stem function
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Stem structure
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Monocot vs Dicot Stems

• Monocot
• Vascular bundles scattered throughout stem
• Three tissues
• Vascular
• Epidermis
• Ground tissue
• Dicot
• Vascular tissue arranged in a cylinder (ring
  pattern)
• Parenchyma cells inside vascular bundles called
  Pith
• Parenchyma cells outside vascular bundle called
  Cortex

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Stem types
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Monocot Dicot
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Dicot Stem
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Monocot Stem
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Growth of Stems

• Primary
• Growth that occurs at the end of plants (increase
  length)
• Apical meristem
• Secondary
• Increase in width (lateral growth)
• Lateral meristematic tissue called vascular and
  cork cambium

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Secondary growth
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Formation

• Wood
• Formation of rings
• Center of tree is old xylem
• Heartwood? center and dark b/c no longer filter
  impurities
• Sapwood? active fluid transport
• Bark
• All tissues outside the vascular cambium phloem,
  cork cambium and cork
• Expansion of vascular cambium causes oldest
  tissue to split and fragment
• Cork cambium produces the protective layer of
  bark that falls off

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wood
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bark
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Leaves

• Structure
• Optimized for absorbing light and carrying out
  photosynthesis
• Cuticle waterproof outer covering
• Vascular bundles surrounded by parenchyma and
  sclerenchyma cells
• Blades? flattened sections that collect sunlight
• Petiole? thin stalk that attaches the blade to
  the stem

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Leaves

• Functions
• Photosynthesis
• Transpiration
• Gas Exchange

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Leaves

• Function
• Photosynthesis
• Mesophyll? packed with chloroplasts and carries
  out photosynthesis
• Transports carbohydrates to phloem
• Palisade mesophyll? absorbs much of the light
• Spongy mesophyll? air spaces connect to exterior
  through stomata

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Leaves

• Functions
• Photosynthesis cont
• Stomata? opening allows carbon dioxide and oxygen
  to diffuse in and out of leaf
• 2 guard cells control opening and closing of
  stomata
• Open during dayphotosynthesis
• Closed at night water loss

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Leaves

• Functions
• Transpiration? water loss from a plant through
  its leaves
• Water is replaced by water drawn into leaf from
  xylem

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Leaves

• Functions
• Gas Exchange
• Between air spaces in the spongy mesophyll and
  opening stomata
• Plants keep stomata open just enough to allow
  photosynthesis to take place

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Transport of Water

• Capillary Action
• Transpiration

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Transport in Plants

• Capillary Action
• Tendancy of water to rise in a thin tube
• Water forms H bonds with one another

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Transport in Plants

• Transpiration
• Major force in water transport
• Controlled by water moving into and out of spongy
  mesophyll
• Water enters guard cells open stomata
• Water lost guard cells close stomata

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Nutrient Transport

• Phloem
• Pump sugars into a plants fruits or into roots
• Pumps sugars back out in spring to aid in growth

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Nutrient Transport

• Source to Sink
• Source? where sugars are produced
• Sink? where sugars are stored
• When nutrients are removed from the phloem system
  the change in concentration causes a mavement of
  fluid in that direction