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?