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Horticulture Science
Lesson 8
Understanding Stem
Anatomy
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.
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.
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.
Function of a Stem
• Stems
leaves
collect
• Stems
support the leaves. They hold the
in the most efficient position to
sunlight.
are also used for food storage.
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
–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.
– On the
outside of
both terminal
and lateral
buds are
small
protective
structures
called bud
scales.
–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.
Internal Structures of a Stem
• In
MONOCOTS
the stem
structure is
in bundles.
Internal Structure of a Stem
• In dicots,
the
structure is
made of
rings.
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.
Internal Structure
• Cambium-Builds new xylem and
phloem cells.
• In dicots, this causes the plant go
grow in girth….trees!
• In monocots, the cambium doesn’t
circle the outside of the plant, so it
doesn’t continue to grow past
maturity.
The Pith
• The pith is the
very center of the
stem, it is from
the Old English
word meaning,
“pit of the fruit”
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?
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.