Plant Structures Roots, Stems, and Leaves

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Plant StructuresRoots, Stems, and Leaves

• Acton Science
• Mr. LeBlanc

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Specialized Tissues in Plants

• Plants are as successful if not more successful
  than animals
• Seed plants have three main structures
• Roots
• Stems
• Leaves
• Linked together by various means

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Specialized Tissues in Plants

• 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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Specialized Tissues in Plants

• 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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Specialized Tissues in Plants

• Leaves
• Main photosynthetic systems
• Suseptable to extreme drying
• Sight of oxygen/carbon dioxide intake and release

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Specialized Tissues in Plants

• Plant tissue systems
• Exist within the root, stems, and leaves
• Dermal tissue
• Vascular tissue
• Ground tissue

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Specialized Tissues in Plants

• 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

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Specialized Tissues in Plants

• Vascular Tissue
• Transport System
• Subsystems
• Xylem
• Phloem
• Subsystems are used to carry fluids throughout
  plant

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Specialized Tissues in Plants

• Xylem
• Two types
• Seed plants
• Angiosperms
• Tracheid long narrow cells
• Walls are connected to neighboring cells
• Will eventually die
• Vessel Element wider that trachieds

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Specialized Tissues in Plants

• Phloem
• Sieve Tube Elements
• Cells arranged end to end
• Pump sugars and other foods
• Companion Cells
• Surround sieve tube elements
• Support phloem cells

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Specialized Tissues in Plants

• Ground Tissue
• Cells between dermal and vascular tissue
• Parenchyma
• Thin cell walls, large vacuoules
• Collenchyma
• Strong, flexible cell walls
• Sclerenchyma
• Extremely thick, rigid cell walls

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Specialized Tissues in Plants

• Plant Growth
• Meristems tissues responsible for growth
• Undifferentiated cells
• Apical Meristem
• Produce growth increased length
• Differentiation
• Cells will assume roles in the plant
• Flower Development
• Starts in the meristem

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Roots

• Types of Roots
• Taproots
• Found in dicots
• Long, thick root
• Hickory and oak trees
• Fibrous roots
• Found in monocots
• No single root larger than any other
• Many thin roots

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Roots

• Root Structure
• Outside layer
• Epidermis
• Root hairs
• Cortex
• Central cylinder vascular system
• Root Cap cellular production
• Key role in water/mineral transport

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Roots

• Root Functions
• Anchor plant
• Absorb water
• Absorb nutrients

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Roots

• Plant Nutrient Uptake
• Soil type determines plant type
• Plant requirements
• Oxygen, CO2
• Nitrogen
• Phosphorus
• Postassium
• Magnesium
• Calcium
• Trace elements

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Roots

• Active Transport in Plants
• Root hairs use ATP
• Pump minerals from soil
• Causes water molecules to follow by osmosis
• Vascular Cylinder
• Casparian Strip water retention
• Root Pressure
• Forces water up into the plant

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Stems

• Stem Structure
• Produce leaves, branches, and flowers
• Hold leaves up
• Transport substance between roots and leaves
• Essential part of transport system
• Function in storage and photosynthesis

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Stems

• Xylem and phloem major tubule systems
• 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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Stems

• Stem Types
• Monocot vascular bundles are scattered
  throughout
• Distinct epidermis
• Dicot vascular tissue arranged in a cylinder
• Pith parenchyma cells inside the ring

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Stems

• Stem Growth
• Primary growth new cells produced at the root
  tips and shoots
• Increases the length
• Secondary growth increase in stem width
• Vascular cambium produces tissue and increases
  thickness
• Cork cambium produces outer covering of stems

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Stems

• Formation of Vascular Cambium
• Xylem and phloem bundles present intially
• Secondary growth initiates production of a thin
  layer
• The vascular cambium divides
• Produces new xylem and phloem

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Stems

• Formation of wood
• Wood layers of exlem
• Produced year after year
• Results from the older xylem not conducting water
  heartwood
• Becomes darker with age
• Sapwood surrounds heartwood

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Roots

• Formation of Bark
• All the tissues outside the vascular cambium
• Consists of outermost layers of dead cork
• Water proof

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Leaves

• Main sight of photosynthesis
• Consist of
• Blade thin flattened section
• Petiole stalk that attaches stem to blade
• Covered by epidermis and cuticle
• Create water proof barrier

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Leaves

• Leaf Functions
• Photosynthesis occurs in the mesophyll
• Palisade mesophyll absorb light
• Spongy mesophyll beneath palisede level
• Stomata pores in the underside of the leaf
• Guard Cells Surround the stomata

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Leaves

• Transpiration
• Loss of water through its leaves
• Replaced by water drawn into the leaf

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Leaves

• Gas Exchange
• Take in CO2 and release O2
• Can also do the opposite How?
• Gas exchange takes place at the stomata
• Not open all the time
• Stomata is controlled by water pressure in guard
  cells

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Transport in Plants

• Water Transport
• Active transport and root pressure
• Cause water to move from soil to roots
• Capillary action
• Combined with active transport and root pressure,
  moves materials throughout the plant

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Transport in Plants

• Capillary Transport
• 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

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Transport in Plants

• Transpiration
• 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

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Transport in Plants

• Controlling Transpiration
• Open the stomata increase water loss
• Close the stomata decrease water loss

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Transport in Plants

• Transpiration and Wilting
• 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

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Transport in Plants

• Nutrient Transport
• Most nutrients are pushed through plant
• Nutrient movement takes place in phloem
• Source to Sink
• Source any cell that produces sugars
• Sink any cell where sugars are used
• Pressure-flow Hypothesis