Stems
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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)

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Stems

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Stems

Stems

S7-3-1


2 functions of a stem

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

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 stem

Parts of a woody stem

Outer 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

Uses of stems

  • Wood—building houses, furniture

    FYI: ¾ used for construction

  • 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)

  • Paper products—including cardboard

  • Fuel—many homes burn wood for heat

    • FYI: 1 ton/year used for fuel

Willow tree


Specialized stems 1

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


Stems

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!!


Stems

Specialized stems #3

We like to eat some stems!

Asparagus

Celery

Sugar cane

Rhubarb


Stems

Specialized stems #4

Our most

common tuber . . .

Tubers—underground stems used for food storage and reproduction

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

under-

ground

POTATOES!

The tubers may then be dug up and eaten


Questions answer on a separate piece of paper

Questions: Answer on a separate piece of paper

  • 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?


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