Vascular Stems

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Vascular Stems

• D.L. Mowery
• Douglass High School

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Stems

• Stems have many functions
• Support the leaves (hold them up)
• Transport Water and Sugars
• Provide Storage

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Basic Stem Structures

• End of the internode where one or more leaves are
  attached
• Stem segments

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The Function of Herbaceous Stem Tissues

• Epidermis outer protective layer
• Cortex ground tissue.composed of parenchyma
  cells (storage cells)
• Sclerenchyma strength tissue. prevents xylem
  and phloem from kinking
• Vascular Bundle made up of the xylem, phloem
  and sclerenchyma
• Xylem transports water
• Phloem transport sugars

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Herbaceous Monocot Stem X-section
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Herbaceous Dicot X-section
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Herbaceous Dicot Root
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Woody Dicot X-section
Sapwood
Heartwood
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Coleus Stem Tip
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Epidermal Hairs

• Leaf hairs in plants have several functions
• One of them is to provide protection from
  evaporation
• A leaf with hairs therefore loses much less
  moisture through surface evaporation in windy
  weather and thus less water is drawn from the
  leaf
• But leaf hairs also play an important role in
  protecting the plant from parasites
• They can either contain antibodies to protect the
  plant from herbivores

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Translocation

• Movement of sucrose and other organic materials
  from one place to another, primarily through the
  phloem
• Concentrations drive this process
• Typically in any location where sucrose is in
  high concentration
• Concentration or pressure difference causes
  sucrose to diffuse toward and into the phloem of
  the leaf and hence to the phloem of the stem
• Sucrose moves up and down the phloem in the
  direction of the lower concentration

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Translocation
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Translocation

• The main sugar transportation tissue in plants is
  the Xylem. Xylem is made up of Tracheids and
  Vessel Members

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The End.