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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)

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Stems

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  1. Stems S7-3-1

  2. 2 Functions of a Stem • Transport water, minerals, and food between roots and leaves (via phloem and xylem) • Hold leaves up to receive sunlight

  3. 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)

  4. 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

  5. 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

  6. 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

  7. 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!!

  8. Specialized stems #3 We like to eat some stems! Asparagus Celery Sugar cane Rhubarb

  9. 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

  10. 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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