Horticulture Science Lesson 8 Understanding Stem Anatomy

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Horticulture Science Lesson 8Understanding Stem
Anatomy
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Monocots vs. Dicots

• Way we classify plants
• Monocot seeds have one seed leaf, Dicots have two
  seed leaves.
• Monocots parts are in multiples of 3, dicots are
  in multiples of 4 or 5.
• They also have different stem systems.

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What are the functions of a stem?

• Stems move water and minerals up from the roots
  to the leaves.
• They also move food made from photosynthesis down
  to the roots.

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How?

• Water molecules are attracted to each other like
  magnets.
• This is called COHESION.
• Water molecules in plants travel through the
  XYLEM, a tube that runs through the stem by
  cohesion.

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Function of a Stem

• Stems support the leaves. They hold the leaves in
  the most efficient position to collect sunlight.
• Stems are also used for food storage.

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External Parts of a Stem

• Lenticels- breathing pores
• Terminal Bud- The end of the stem where growth is
  taking place.
• Bud scale scars- Indicates a terminal bud has
  been located there.
• Distance between the two shows one year of growth

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• The leaf is attached to the stem at the node.
• The area between leaves is called an internode.
• At the node, just above where the leaf is
  attached, there is always a side bud called the
  lateral bud.

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• On the outside of both terminal and lateral buds
  are small protective structures called bud
  scales.

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• When the leaf falls off of the stem, it leaves
  behind a small scar just below the lateral bud.
• This scar is called the leaf scar.

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Internal Structures of a Stem

• In MONOCOTSthe stem structure is in bundles.

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Internal Structure of a Stem

• In dicots, the structure is made of rings.

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Internal Structure

• Xylem- Water and nutrients move UP the plant from
  the roots to the leaves through cohesion.
• Phloem-Food and energy manufactured through
  photosynthesis moves from the leaves to the
  roots.

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Internal Structure

• Cambium-Builds new xylem and phloem cells.
• In dicots, this causes the plant go grow in
  girth.trees!
• In monocots, the cambium doesnt circle the
  outside of the plant, so it doesnt continue to
  grow past maturity.

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The Pith

• The pith is the very center of the stem, it is
  from the Old English word meaning, pit of the
  fruit

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Review

• What is one way we classify monocots and dicots
  differently?
• What is the function of the lenticels?
• What is the process called that helps water
  travel upward through the xylem?
• What is the purpose of the phloem?
• What does the cambium do?

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Task Dissect a Flower!

• You will need white paper, flower, tape, marker,
  and a knife.
• Cut the flower in half.
• With one half, remove a petal, a stamen and
  pistil. Tape over it, label them and describe
  their function and the process of pollination.
• Tape the other half to your paper and label the
  same parts, but also the sepal and any parts of
  the stem you can identify.