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Angiosperms VI

Angiosperms VI. Secondary Growth In Stems. What is secondary growth?. Growth in “girth” of woody plants Tissues derived from cambial layers VASCULAR CAMBIUM produces secondary xylem and secondary phloem CORK CAMBIUM (phellogen) produces cork (phellem) and phelloderm tissues.

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Angiosperms VI

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  1. Angiosperms VI Secondary Growth In Stems

  2. What is secondary growth? • Growth in “girth” of woody plants • Tissues derived from cambial layers • VASCULAR CAMBIUM • produces secondary xylem and secondary phloem • CORK CAMBIUM (phellogen) • produces cork (phellem) and phelloderm tissues

  3. Typical Woody Eudicot Stem (overview) • Periderm or “bark” • Vascular cambium • Secondary xylem • Pith

  4. Woody Eudicot Stem

  5. Typical Woody Eudicot Stem(detail) • Secondary xylem • Vascular cambium • Rays • Secondary phloem (including phloem fibers) • Cortex

  6. Secondary Xylem (angiosperms) • Vessels • Fibers and tracheids • Wood rays • Growth rings (annual rings)

  7. Secondary Xylem(“up close and personal”) • Fibers • Tracheids • Vessels • Ray parenchyma

  8. “Growth Rings” • Spring (Early) Wood • first cells produced by the vascular cambium • large cells (good growing conditions) • Summer (Late) Wood • smaller cells produced toward the end of the growing season • poor conditions (cooler, drier) • Radical change in cell size allows for recognition of annual “growth rings”

  9. Bristlecone Pine(oldest of tree species in North America) 4900 + years old

  10. Oak Wood in Section Note: thick, multiseriate wood rays

  11. Other Variations • Heartwood • darker in color • occupies center of the stem, more dense (stronger) • deposit of waste products such as resins, gums, oils, and tannins • Sapwood • lighter in color • outer layers, less dense (weaker) • contains the sap (dissolved nutrients and water)

  12. Woody Stem and Periderm sapwood heartwood

  13. Woody Twigs • Terminal bud with bud scales • Axillary buds • Lenticels • Leaf scar

  14. Twig Structures

  15. Lenticels • Pores in the cork layers which allow for gas exchange in the periderm

  16. Uses of Secondary Growth • Wood Products • Various uses based on the density of the wood (often in lbs./cubic foot) • Furniture, baseball bats, plywood, pulp products, musical instruments, particle board, artistic pieces, fuel • Other Products • rope, cinnamon, dyes, drugs (quinine), charcoal, cork, maple syrup

  17. CorkHarvesting

  18. Making MapleSyrup 30-50 gallons of sap to make 1 gallon of syrup

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