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Plant Structure and Function

Plant Structure and Function. Stem. Support leaves Transport materials Provide storage. Types of Stems. Types of Stems. Woody or nonwoody (herbaceous) Stolons Grow along soil surface Produce new plants Tuber Store energy Cacti Green fleshy stems Store water and photosynthesis

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Plant Structure and Function

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  1. Plant Structure and Function Stem

  2. Support leaves • Transport materials • Provide storage

  3. Types of Stems

  4. Types of Stems • Woody or nonwoody (herbaceous) • Stolons • Grow along soil surface • Produce new plants • Tuber • Store energy • Cacti • Green fleshy stems • Store water and photosynthesis • Modified for protection

  5. Stem Structures • Did you know that a sign nailed 2m (7ft) high on a tree will remain at that height, even though the tree may grow much taller?

  6. Stem Structure • Grow in length only at tip • Apical meristems • Primary tissues • Lateral meristems • Secondary growth (diameter)

  7. Stem Features • Node • Leaf attaches to stem • Internode • Space between nodes • Lateral bud • Bud • Stem or leaf • Apical meristem enclosed by bud scales

  8. Winter Identification of Trees

  9. Primary Growth in Stems • Apical meristem • Dermal, protect plant • Ground, cortex and pith • Pith located at center of stem • Vascular tissue, occurs in bundles • Xylem (inside) and phloem (outside) • Monocots v.b. scattered • Dicots v.b. rings

  10. Monocot and Dicot Vascular Bundles

  11. Secondary Growth in Stems • Stems increase in thickness • Cell division in vascular cambium • Dicot and gymnosperms • Stem forms b/w xylem and phloem in vascular bundle • Vascular cambium • produces 20 xylem (inside) and phloem (outside) • 20 xylem represents the wood of the plant • New cambium cells increases stems diameter

  12. Stem Growth pg581 • http://academic.kellogg.edu/herbrandsonc/bio111/stems.htm

  13. Older xylem stop producing water • Darken wood called heartwood • Will increase in diameter • Lighter – colored wood called sapwood • Stays about the same • Phloem near outside of stem • Bark • Cork, cork cambium, and phloem • Protective layer • Cork cells die at maturaty • Cannot elongate and will rupture as stem increases in diameter • Bark pattern (maples and oaks)

  14. Cross Section of Woody Stem

  15. Annual Rings • Springwood • Water plentiful • Vas. Cambium form new xylem cells • Wide and thin cell walls • Summerwood • Water scarce • Vas. Cambium forms smaller thicker cells • Difference causes a change in appearance • One ring each year used to determine age

  16. Stem Functions • Transport nutrients and water • Store these nutrients • Support leaves

  17. Translocation • Movement of carbohydrates through a plant • Source to sink • Source (storage) • Sink (usage) • Pressure – flow hypothesis • Actively transported into sieve tubes • Water transported by osmosis

  18. Pressure – Flow Hypothesis

  19. Transport of Water • Water and mineral nutrients occur in xylem • Water is constantly evaporating from plant • Stomata • Transpiration

  20. Cohesion – tension theory • Water is pulled up the stem xylem by the strong attraction of water molecules to each other and the wall of the xylem • Cohesion and adhesion properties • Tug – n – pull, from roots up the xylem

  21. Cohesion – Tension Theory

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