Transcript S7-3-1 Stems

Stems
S7-3-1
2 Functions of a Stem

Transport water,
minerals, and food
between roots and
leaves (via phloem
and xylem)

Hold leaves up to
receive sunlight
2 types of stems

Herbaceous-green and
soft, bendable (sunflower,
peas, grass)

Woody—contain wood
(hard substance made of
thickened xylem); rigid
and strong (roses,
maples, firs)
Outer bark—old phloem, gives protection
Parts of a woody stem
Phloem—innermost bark
Cambium—where growth occurs
Xylem
-Sapwood—active xylem
-Heartwood—clogged xylem that
.
doesn’t transport but
.
gives support
Pith—soft center core; contains
.
large, thin-walled cells that
.
store water and food
Uses of stems
 Wood—building houses, furniture
FYI: ¾ used for construction
 Paper products—including cardboard
 Fuel—many homes burn wood for heat
FYI: 1 ton/year used for fuel

Medicines:

Aspirin—pain reliever, from willow bark



Hydrocortisone—reduces swelling, from yam
tubers
Taxol—cancer treatment drug, from yew bark
Foods (more info on this later)
Willow tree

FYI: Many Native American tribes chewed on
willow bark for its pain relieving properties long
ago
Specialized stems #1

Allows plant to spread to new places

Ex. Vines, morning glories, creeping jennies
Stolon: A stem that grows horizontally
above the ground and produces roots and
shoots to create new plants. Also called
runners.
Ex. Strawberries
Specialized stems #2
• Water storage—some plants store large
amounts of water in their stem to prepare for dry
conditions
• Ex. Cacti
• Food storage . . .
It’s such a big category,
it needs a separate page!!
Specialized stems #3
We like to eat some stems!
Celery
Sugar cane
Rhubarb
Asparagus
Specialized stems #4
Tubers—underground stems used
for food storage and reproduction
Our most
common tuber . . .
Ex. potato (the ‘eyes’ will grow new
stems)
The stem “swells” to
store food for the plant
The green plant grows
above ground with
tubers
growing
underground
POTATOES!
The tubers may then
be dug up and eaten
Questions: Answer on a separate piece of paper
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10.
List the 2 functions of a stem.
What type of stem does a tulip have?
What type of stem does an oak have?
What type of vascular tissue is bark made of?
What is the difference between heartwood and sapwood?
List 3 uses of stems (not foods).
Why do cacti store a great deal of water?
Out of the 4 listed, name your 2 favorite “stem foods.”
Why do some plants use tubers?
Why does a plant with a longer stem have a competitive
advantage?