Stems S7-3-1
Jan 01, 2016
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)
Parts of a woody stemOuter bark—old phloem, gives protection
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
Medicines: Aspirin—pain reliever, from willow bark
FYI: Many Native American tribes chewed on willow bark for its pain relieving properties long ago
Hydrocortisone—reduces swelling, from yam tubers
Taxol—cancer treatment drug, from yew bark
Foods (more info on this later)
WoodWood—building houses, furniture—building houses, furnitureFYI: ¾ used for constructionFYI: ¾ used for construction
Paper productsPaper products—including cardboard—including cardboard FuelFuel—many homes burn wood for heat—many homes burn wood for heat
FYI: 1 ton/year used for fuelFYI: 1 ton/year used for fuel
Willow
tree
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 storageWater storage—some plants store large —some plants store large amounts of water in their stem to prepare for dry amounts of water in their stem to prepare for dry conditionsconditions• Ex. CactiEx. Cacti
• Food storage . . .Food storage . . .
It’s such a big category, It’s such a big category, it needs a separate page!!it needs a separate page!!
Specialized stems #3
We like to eat some stems!
Asparagus
Rhubarb
Celery
Sugar cane
Specialized stems #4Tubers—underground stems used for food storage and reproductionEx. 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 under-ground
The tubers may then be dug up and eaten
Our most common tuber . . .
POTATOES!
Questions: Answer on a separate piece of paper
1. List the 2 functions of a stem.2. What type of stem does a tulip have?3. What type of stem does an oak have?4. What type of vascular tissue is bark made of?5. What is the difference between heartwood and sapwood?6. List 3 uses of stems (not foods).7. Why do cacti store a great deal of water?8. Out of the 4 listed, name your 2 favorite “stem foods.”9. Why do some plants use tubers?10. Why does a plant with a longer stem have a competitive
advantage?